Of the laws of chance, or, A method of calculation of the hazards of game plainly demonstrated and applied to games at present most in use : which may be easily extended to the most intricate cases of chance imaginable. Arbuthnot, John, 1667-1735. 1692 Approx. 67 KB of XML-encoded text transcribed from 61 1-bit group-IV TIFF page images. Text Creation Partnership, Ann Arbor, MI ; Oxford (UK) : 2004-03 (EEBO-TCP Phase 1). A25748 Wing A3602 ESTC R31565 12165155 ocm 12165155 55286 This keyboarded and encoded edition of the work described above is co-owned by the institutions providing financial support to the Early English Books Online Text Creation Partnership. This Phase I text is available for reuse, according to the terms of Creative Commons 0 1.0 Universal . The text can be copied, modified, distributed and performed, even for commercial purposes, all without asking permission. Early English books online. (EEBO-TCP ; phase 1, no. A25748) Transcribed from: (Early English Books Online ; image set 55286) Images scanned from microfilm: (Early English books, 1641-1700 ; 1495:1) Of the laws of chance, or, A method of calculation of the hazards of game plainly demonstrated and applied to games at present most in use : which may be easily extended to the most intricate cases of chance imaginable. Arbuthnot, John, 1667-1735. [24], 93 p. Printed by Benj. Motte, and sold by Randall Taylor ..., London : 1692. Attributed to Arbuthnot by Wing and NUC pre-1956 imprints. Reproduction of original in the British Library. Created by converting TCP files to TEI P5 using tcp2tei.xsl, TEI @ Oxford. Re-processed by University of Nebraska-Lincoln and Northwestern, with changes to facilitate morpho-syntactic tagging. Gap elements of known extent have been transformed into placeholder characters or elements to simplify the filling in of gaps by user contributors. 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Copies of the texts have been issued variously as SGML (TCP schema; ASCII text with mnemonic sdata character entities); displayable XML (TCP schema; characters represented either as UTF-8 Unicode or text strings within braces); or lossless XML (TEI P5, characters represented either as UTF-8 Unicode or TEI g elements). Keying and markup guidelines are available at the Text Creation Partnership web site . eng Probabilities. Games of chance (Mathematics) Game theory. 2003-06 TCP Assigned for keying and markup 2003-07 Apex CoVantage Keyed and coded from ProQuest page images 2004-01 Emma (Leeson) Huber Sampled and proofread 2004-01 Emma (Leeson) Huber Text and markup reviewed and edited 2004-02 pfs Batch review (QC) and XML conversion OF THE Laws of Chance , OR , A METHOD OF Calculation of the Hazards OF GAME , Plainly demonstrated , And applied to GAMES at present most in Use , Which may be easily extended to the most intricate Cases of Chance imaginable . LONDON : Printed by Benj. Motte , and sold by Randall Taylor near Stationers-Hall , 1692. PREFACE . IT is thought as necessary to write a Preface before a Book , as it is judg'd civil , when you invite a Friend to Dinner , to proffer him a Glass of Hock before-hand for a Whet : And this being maim'd enough for want of a Dedication , I am resolv'd it shall not want an Epistle to the Reader too . I shall not take upon me to determine , whether it is lawful to play at Dice or not , leaving that to be disputed betwixt the Fanatick Parsons and the Sharpers ; I am sure it is lawful to deal with playing at Dice as with other Epidemic Distempers ; and I am confident that the writing a Book about it , will contribute as little towards its Encouragement , as Fluxing and Precipitates do to Whoring . It will be to little purpose to tell my Reader , of how great Antiquity the playing at Dice is , I will only let him know , that by the Aleae Ludus , the Antients comprehended all Games , which were subjected to the determination of mere Chance ; this sort of Gaming was strictly forbid by the Emperor Justinian , Cod. Lib. 3. Tit. 43. under very severe Penalties ; and Photius Nomocan , Tit. 9. Cap. 27. acquaints us , that the Use of this was altogether denied the Clergie of that time . Seneca says very well , Aleator quantò in arte est melior , tantò est nequior ; That by how much the one is more skilful in Games , by so much he is the more culpable ; or we may say of this , as an ingenious Man says of Dancing , That to be extraordinary good at it , is to be excellent in a Fault ; therefore I hope no body will imagine I had so mean a Design in this , as to teach the Art of Playing at Dice . A great part of this Discourse is a Translation from Mons. Hugen's Treatise , De ratiociniis in ludo Aleae , one , who in his Improvements of Philosophy , has but one Superior , and I think few or no Equals . The whole I undertook for my own Divertisement , next to the Satisfaction of some Friends , who would now and then be wrangling about the Proportions of Hazards in some Cases that are here decided . All it requir'd was a few spare Hours , and but little Work for the Brain ; my Design in publishing it , was to make it of more general Use , and perhaps persuade a raw Squire , by it , to keep his Money in his Pocket ; and if , upon this account , I should ineur the Clamours of the Sharpers , I do not much regard it , since they are a sort of People the World is not bound to provide for . You will find here a very plain and easie Method of the Calculation of the Hazards of Game , which a man may understand , without knowing the Quadratures of Curves , the Doctrin of Series's , or the Laws of Centripetation of Bodies , or the Periods of the Satellites of Jupiter ; yea , without so much as the Elements of Euclid . There is nothing required for the comprehending the whole , but common Sense and practical Arithmetick ; saving a few Touches of Algebra , as in the first Three Propositions , where the Reader , without suspicion of Popery , may make use of a strong implicit Faith ; tho I must confess , it does not much recommend it self to me in these purposes ; for I had rather he would enquire , and I believe he will find the speculation not unpleasant . Every man's Success in any Affair is proportional to his Conduct & Fortune . Fortune ( in the sense of most People ) signifies an Event which depends on Chance , agreeing with my Wish ; and Misfortune signifies such an Event contrary to my Wish : an Event depending on Chance , signifies such an one , whose immediate Causes I don't know , and consequently can neither foretel nor produce it ( for it is no Heresie to believe , that Providence suffers ordinary matters to run in the Channel of second Causes ) . Now I suppose , that all a wise Man can do in such a Case is , to lay his Business on such Events , as have the most or most powerful second Causes , and this is true both in the great Events of the World , and in ordinary Games . It is impossible for a Dye , with such a determin'd force and direction , not to fall on such a determin'd side , only I don't know the force and direction which makes it fall on such a determin'd side , and therefore I call that Chance , which is nothing but want of Art ; that only which is left to me , is to wager where there are the greatest number of Chances , and consequently the greatest probability to gain ; and the whole Art of Gaming , where there is any thing of Hazard , will be reduc'd to this at last , viz. in dubious Cases , to calculate on which side there are most Chances ; and tho this can't be done in the midst of Game precisely to an Unite , yet a Man who knows the Principles , may make such a conjecture , as will be a sufficient direction to him ; and tho it is possible , if there are any Chances against him at all , that he may lose , yet when he chuseth the safest side , he may partwith his Money with more content ( if there can be any at all ) in such a Case . I will not debate , whether one may engage another in a disadvantageous Wager . Games may be suppos'd to be a tryal of Wit as well as Fortune , and every Man , when he enters the Lists with another , unless out of Complaisance , takes it for granted , his Fortune and Iudgment , are , at least , equal to those of his Play-Fellow ; but this I am sure of , that false Dice , Tricks of Leger-de-main , &c. are inexcusable , for the question in Gaming is not , Who is the best Iugler ? The Reader may here observe the Force of Numbers , which can be succesfully applied , even to those things , which one would imagin are subject to no Rules . There are very few things which we know , which are not capable of being reduc'd to a Mathematical Reasoning , and when they cannot , it s a sign our Knowledg of them is very small and confus'd ; and where a mathematical reasoning can be had , it 's as great folly to make use of any other , as to grope for a thing in the dark when you have a Candle standing by you . I believe the Calculation of the Quantity of Probability might be improved to a very useful and pleasant Speculation , and applied to a great many Events which are accidental , besides those of Games ; only these Cases would be infinitely more confus'd , as depending on Chances which the most part of Men are ignorant of ; and as I have hinted already , all the Politicks in the World are nothing else but a kind of Analysis of the Quantity of Probability in casual Events , and a good Politician signifies no more , but one who is dexterous at such Calculations ; only the Principles which are made use of in the Solution of such Problems , can't be studied in a Closet , but acquir'd by the Observation of Mankind . There is likewise a Calculation of the Quantity of Probability founded on Experience , to be made use of in Wagers about any thing ; for Example , it is odds , if a Woman is with Child , but it shall be a Boy ; and if you would know the just odds , you must consider the Proportion in the Bills that the Males bear to the Females : The Yearly Bills of Mortality are observ'd to bear such Proportion to the live People as 1 to 30 , or 26 ; therefore it is an even Wager , that one out of thirteen , dyes within a Year ( which may be a good reason , tho not the true one of that foolish piece of Superstition ) , because , at this rate , if 1 out of 26 dyes , you are no loser . It is but 1 to 18 if you meet a Parson in the Street , that he proves to be a Non-Juror , because there is but 1 of 36 that are such . It is hardly 1 to 10 , that a Woman of Twenty Years old has her Maidenhead , and almost the same Wager , that a Town-Spark of that Age has not been clap'd . I think a Man might venture some odds , that 100 of the Gens d'arms beats an equal Number of Dutch Troopers ; and that an English Regiment stands its ground as long as another , making Experience our Guide in all these Cases and others of the like nature . But there are no casual Events , which are so easily subjected to Numbers , as those of Games ; and I believe , there the Speculation might be improved so far , as to bring in the Doctrin of the Series's and Logarithms . Since Gaming is become a Trade , I think it fit the Adventurers should be upon the Square ; and therefore in the Contrivance of Games there ought to be a strict Calculation made use of , that they mayn't put one Party in more probability to gain than another ; and likewise , if a Man has a considerable Venture , he ought to be allow'd to withdraw his Money when he pleases , paying according to the Circumstances he is then in : and it were easie in most Games to make Tables , by the Inspection of which , a Man might know what he was either to pay or receive , in any Circumstances you can imagin , it being convenient to save a part of ones Money , rather than venture the loss of it all . I shall add no more , but that a Mathematician will easily perceive , it is not put in such a Dress as to be taken notice of by him , there being abundance of Words spent to make the more ordinary sort of People understand it . FOR the sake of those who are not vers'd in Mathematicks , I have added the following Explanation of Signs . = Equal . + More , or to be added . − Less , or to be subtracted . × Multiplied . Example . 3 × 4 + 3 − 1 = 14 = 5 / 9 a , is to be read thus , 3 multiplied in 4 more by 3 less by 1 is equal to 14 , which is equal to five ninth parts of a. An Exact METHOD For SOLVING the Hazards of Game . ALthough the Events of Games , which Fortune solely governs , are uncertain , yet it may be certainly determin'd , how much one is more ready to lose than gain . For Example : If one should wager , at the first Throw with one Dye , to throw Six , it 's an accident if he gains or not , but by how much it 's more probable he will lose than gain , is really determin'd by the Nature of the thing , and capable of a strict Calculation . So likewise , if I should play with another on this condition , that the Victory should be to the Three first Games , and I had gain'd one already ; it is still uncertain who shall first gain the third ; yet by a demonstrative reasoning I can estimate both the Value of his expectation and mine , and consequently ( if we agree to leave the Game unperfect ) determin how great a share of the Stakes belong to me , and how much to my Play-fellow ; or if any were desirous to take my place , at what rate I ought to sell it . Hence may arise innumerable Queries among two , three , or more Gamesters ; and since the Calculation of these things is a little out of the common road , and can be oft-times apply'd to good purpose ; I shall briefly here shew how it is to be done , and afterwards explain those things which belong properly to the Dice . In both cases I shall make use of this Principle , Ones Hazard or Expectation to gain any thing , is worth so much , as , if he had it , he could purchase the like Hazard or Expectation again in a just and equal Game . For Example , If one , without my knowledg , should hide in one Hand 7 Shillings , and in his other 3 Shillings , and put it to my choice which Hand I would take , I say this is as much worth to me , as if he should give me 5 Shillings ; because , if I have 5 Shillings , I can purchase as good a Chance again , and that in a fair and just Game . PROPOSITION I. If I expect a or b , either of which , with equal probability , may fall to me , then my Expectation is worth , that is , the half Sum of a and b. THat I may not only demonstrate , but likewise investigate this Rule , suppose the Value of my Expectation be x ; by the former Principle having x , I can purchase as good an Expectation again in a fair and just Game . Suppose then I play with another on these terms ; That every one stakes x , and the Gainer give to the Loser a , this Game is just , and it appears , that at this rate , I have an equal hazard either to get a if I lose the Game , or 2 x − a if I gain ; for in this case I get 2 x , which are the Stakes , out of which I must pay the other a ; but if 2 x − a were worth b , then I have an equal hazard to get a or b ; therefore making 2 x − a = b , , which is the Value of my Expectation . The Demonstration is easie , for having , I can play with another who will stake against it , on this condition , that the Gainer should give to the Loser a ; by this means I have an equal Expectation to get a if I lose , or b if I win ; for in the last case I get a+b the Stakes , out of which I must pay a to my Play-fellow . In Numbers : If I had an equal hazard to get 3 or 7 , then by this Proposition , my Expectation is worth 5 , and it is certain , having 5 , I may have the same Chance ; for if I play with another so that every one stakes 5 , and the Gainer pay to the Loser 3 , this is a fair way of Gaming ; and it is evident , I have an equal hazard to get 3 if I lose , or 7 if I gain . PROP. II. If I expect a , b , or c , either of which , with equal facility , may happen , then the Value of my Expectation is , or the third part of the Sum of a b and c. FOR the Investigation of which , suppose x be the value of my Expectation ; then x must be such , as I can purchase with it the same Expectation in a just Game : Suppose the Conditions of the Game be , that playing with two others , each of us stakes x , and I bargain with one of the Gamesters , if I win , to give him b , and he shall do the same to me ; but with the other , that if I gain , I shall give him c , and vice versâ ; this is fair play : And here I have an equal hazard to get b , if the first win , c if the second , or 3 x − b − c if I gain my self ; for then I get 3 x , viz. the Stakes , of which I give the one b and the other c ; but if 3 x − b − c be equal to a , I have an equal Expectation of a , b , or c ; therefore making 3 x − b − c = a , , which is the Value of my Expectation . After the same method you will find , if I had an equal hazard to get a b c or d , the Value of my Expectation that is the fourth part of the Sum of a b c and d , &c. PROP. III. If the Number of Chances , by which a falls to me , be p , and the Number of Chances , by which b falls , be q , and supposing all the Chances do happen with equal Facility , then the Value of my Expectation is , i. e. the Product of a multiplied in the Number of its Chances added to the Product of b , multiplied into the Number of its Chances , and the Summ divided by the Number of Chances both of a and b. SUppose , as before , x be the Value of my Expectation ; then if I have x , I must be able to purchase with it that same Expectation again in a fair Game : For this I shall take as many Play-fellows as , with me , make up the Number of p+q , of which let every one stake x , so the whole Stake will be px+qx , and every one plays with equal hopes of winning ; with as many of my Fellow-Gamesters as the Number 9 stands for , I make this bargain one by one , that whoever of them gains shall give me b , and if I win , I shall do so to them ; with every one of the rest of the Gamesters , whose Number is p − 1 , I make this bargain , that whoever of them gains , shall give me a , and I shall give every one of them as much , if I gain : It 's evident this is fair play ; for no Man here is injur'd ; and in this case I have q Expectations to gain b , and p − 1 Expectations to gain a , and 1 Expectation ( viz. when I win my my self ) to get px+qx − bqap+a ; for then I am to deliver b to every one of the q Players , and a to every one of the p − 1 Gamesters , which makes ab+pa − a ; if therefore qx+bx − ba − ap+a were equal to a , I would have p Expectations of a ( since just now I had p − 1 Expectations of it ) and q Expectations of b , and so would have just come to my first Expectation ; therefore putting px+qx − bq − ap+a = a , then is In Numbers : If I had 3 Chances to gain for 13 , and 2 for 8 , by this Rule , my Hazard is worth 11 ; for 13 multiplied by 3 gives 39 , and 8 by 2 16 , these two added , make 55 , divided by 5 is 11 , and I can easily shew , if I have 11 , I can come to the like Expectation again ; for playing with four others , and every one of us staking 11 , with two of them I make this Bargain , that whoever gains shall give me 8 , and I shall too do so to them ; with the other two I make this Bargain , that whoever gains shall give me 13 , and I them as much if I gain : It appears , by this means I have two Expectations to get 8 , viz. if any of the first two gain , and 3 Expectations to get 13 , viz. if either I or any of the other two gain ; for in this case I gain the Stakes , which are 55 , out of which I am oblig'd to give the first two 8 , and the other two 13 , and so there remains 13 for my self . PROP. IV. That I may come to the Question propos'd , viz. The making a just Distribution amongst Gamesters , when their Hazards are unequal ; we must begin with the most easie Cases . SUppose then I play with another , on condition that he who wins the three first Games shall have the Stakes , and that I have already gain'd two , I would know , if we agree to break off the Game , and part the Stakes justly , how much falls to my share ? The first thing we must consider in such Questions is , the Number of Games that are wanting to both : For Example , If it had been agreed betwixt us , that he should have the Stakes who gain'd the first 20 Games , and if I had gain'd already 19 , and my Fellow-Gamester but 18 , my Hazard is as much better than his in that Case , as in this proposed , viz ? When of 3 Games I have 2 , and he but 1 , because in both cases there 's 2 wanting to him , and 1 to me . In the next place , to find the portion of the Stakes due to each of us , we must consider what would happen if the Game went on ; it is certain , if I gain the first Game , I get the Stake , which I call a ; but if he gain'd , both our Lots would be equal , and so there would fall to each of us ½ a ; but since I have an equal Hazard to gain or lose the first Game , I have an equal Expectation to gain a , or ½ a , which , by the first Proposition , is as much worth as the half Sum of both , i. e. ¾a , so there is left to my Fellow-Gamester ¼ a ; from whence it follows , that he who would buy my Game , ought to pay me for it ¾ a ; and therefore , he who undertakes to gain one Game before another gains two , may wager 3 to 1. PROP. V. Suppose I want but one Game , and my Fellow-gamester three , it is required to make a just Distribution of the Stake : LET us here likewise consider in what state we should be , if I or he gain'd the first Game ; if I gain , I have the Stake a , if he , then he wants yet 2 Games , and I but 1 , and therefore we should be in the same condition which is supposed in the former Proposition ; and so there would fall to my share , as was demonstrated there , ¾ a ; therefore with equal facility there may happen to me a , or ¾ a , which , by the First Proposition , is worth ⅞ a , and to my Fellow-Gamester there is left 1 / 8 a , and therefore my Hazard to his is as 7 to 1. As the Calculation of the former Proposition was requisite for this , so this will serve for the following . If I should suppose my self to want but one Game , and my Fellow four ( by the same Method ) you will find 15 / 16 of the Stake belongs to me , and 1 / 16 to him . PROP. VI. Suppose I want two Games , and my Fellow-Gamester three . THen by the next Game it will happen , that I want but one , and he three , which ( by the preceding Proposition ) is worth ⅞ a ; or that we should both want two , whence there will be ½ a due to each of us ; now I being in an equal probability to gain or lose the next Game , I have an equal Hazard to gain ⅞ a or ½ a , which , by the First Proposition is worth 11 / 16 a , and so there are eleven parts of the Stakes due to me , and five to my Fellow . PROP. VII . Let us suppose I want two Games , and my Fellow four . IF I gain the next Game , then I shall want but one , and my Fellow four ; but if I lose it , then I shall want two , and he three : So I have an equal Hazard for gaining 15 / 16 a , or 11 / 16 a , which , by the First , is worth 13 / 16 a : So it appears , that he who is to gain two Games for the others four , is in a better condition than he who is to gain one for the others two ; for my share in the first Case is ¾ a or 12 / 16 a , which is less than 13 / 16 , my share in the last . PROP. VIII . Let us suppose three Gamesters , whereof the first and second want 1 Game , but the third 2. TO find the share of the first , we must consider what would happen if either he , or any of the other two gain'd the first Game ; if he gains , then he has the Stake a ; if the second gain , he has nothing ; but if the third gain , then each of them would want a Game , and so ⅓ a would be due to every one of them . Thus the first Gamester has one Expectation to gain a , one to gain nothing , and one for ⅓ a ( since all are in an equal probability to gain the first Game ) which by the second Proposition is worth 4 / 9 a : Now since the second Gamesters Condition is as good , his Share is likewise 4 / 9 a , and so there remains to the third 1 / 9 a , whose Share might have been as easily found by its self . PROP. IX . In any Number of Gamesters you please , amongst whom there are some who want more , some fewer Games : To find what is any ones Share in the Stake , we must consider , what would be due to him , whose Share we investigate , if either he , or any of his Fellow-Gamesters should gain the next following Game ; add all their Shares together , and divide the Sum by the Number of the Gamesters , the Quotient is his Share you were seeking . SUppose three Gamesters , A B and C , A wants 1 Game , B 2 , and C likewise 2 , I would find what is the Share of the Stake due to B , which I shall call q. First we must consider what would fall to B's share , if either he , A , or C , wins the next Game ; if A wins , the Game is ended , so he gets nothing ; if B himself gain , then he wants 1 Game , A 1 , and C 2 ; therefore , by the former Proposition , there is due to him in that Case 4 / ●q , then if C gains the next Play , then A and C would want but 1 , and B 2 ; and therefore , by the Eigth Proposition , his Share would be worth 1 / 9q ; add together what is due to B in all these three Cases , viz. o4 / 9q , 1 / 9q , the Sum is 5 / 9q , which being divided by 3 , the Number of Gamesters gives 5 / 27q , which is the Share of B sought for : The Demonstration of this is clear from the Second Proposition , because B has an equal Hazard to gain o 4 / 9 q or 1 / 9q , that is , , i. e. 5 / 27q ; now it 's evident the Divisor 3 is the Number of the Gamesters . To find what is due to one in any Case , viz. if either he , or any of his Fellow-Gamsters win the following Game ; we must consider first the more simple Cases , and by their help the following ; for as this Case could not be solv'd before the Case of the Eighth Proposition was calculated , in which , the Games wanting were 1 , 1 , 2 ; so the Case , where the Games wanting are 1 , 2 , 3 , cannot be calculated , without the Calculation of the Case , where the Games wanting are 1 , 2 , 2 , ( which we have just now perform'd ) and likewise of the Case , where the Games wanting are 1 , 1 , 3 , which can be done by the Eighth : And by this means you may reckon all the Cases comprehended in the following Tables , and an infinite number of others . As for the Dice ; these Questions may be proposed , at how many Throws one may wager to throw 6 , or any Number below that , with one Dye ; How many Throws are required for 12 upon two Dice ; or 18 on 3 ; and several other Questions to this purpose . For the resolving of which , it must be consider'd , that in one Dye there are six different Throws , all equally probable to come up ; for I suppose the Dye has the exact figure of a Cube : On Two Dice there are 36 different Throws ; for in respect to every Throw of One Dye , any One Throw of the 6 of the other Dye may come up ; and 6 times 6 make 36 : In Three Dice there are 216 different Throws ; for in relation to any of the 36 Throws of Two Dice , any one of the six of the Third may come up ; and 6 times 36 make 216 : So in Four Dice there are 6 times 216 Throws , that is , 1296 : And so forward you may reckon the Throws of any Number of Dice , taking always , for the addition of a new Dye , 6 times the Number of the preceeding . Besides , it must be observ'd , that in Two Dice there is only one way 2 or 12 can come up ; two ways that 3 or 11 can come up ; for if I shall call the Dice A and B to make 3 , there may be 1 in A and 2 in B , or 2 in A and 1 in B ; so to make 11 , there may be 5 in A or 6 in B , or 6 in A and 5 in B ; for 4 there are three Chances , 3 in A and 1 in B , 3 in B and 1 in A , or 2 as well in A as B ; for 10 there are likewise three Chances ; for 5 or 9 there are four Chances ; for 6 or 8 five Chances ; for 7 there are six Chances . In 3 Dice there are found for 3 or 18 1 4 or 17 3 5 or 16 6 6 or 15 10 7 or 14 15 8 or 13 21 9 or 12 25 10 or 11 27 PROP. X. To find at how many times one may undertake to throw 6 with One Dye . IF any should undertake to throw 6 the first time , it 's evident there 's one Chance gives him the Stake , and five which give him nothing ; for there are 5 Throws against him , and only 1 for him : Let the Stake be call'd a , then he has one Expectation to gain a , and five to gain nothing , which , by the Second Proposition , is worth 1 / 6 a , and there remains for the other ⅚ a ; so he who undertakes , with one Dye , to throw 6 the first time , ought to wager only 1 to 5. 2. Suppose one undertake , at two Throws of 1 Dye , to throw 6 , his Hazard is calculated thus ; if he throw 6 at the first he has a the Stake , if he do not , there remains to him one Throw , which , by the former Case , is worth 1 / 6 a ; but there is but one Chance which gives him 6 at the first Throw , and five Chances against him ; so there is one Chance which gives him a , and five which give him 1 / ● a , which , by the Second Proposition , is worth 11 / 36 a , so there remains to his Fellow-Gamester 2● / 3● a ; so the Value of my Expectation to his , is as 11 to 25 , i. e. less than 1 to 2. By the same method of calculation , you will find , that his Hazard who undertakes to throw 6 at three times with one Dye , is 91 / 216 a ; so that he can only lay 91 against 125 , which is something less than 3 to 4. He who undertakes to do it at four times , his Hazard is 671 / 1296 a , so he may wager 671 against 625 , that is , something more than 1 to 1. He who undertakes to do it at five times , his Hazard is 4651 / 7776 a , so he can wager 4651 against 3125 , that is something less than 3 to 2. His Hazard who undertakes to do it 6 times , is 3●031 / 45656 a , and he can wager 31031 against 15625 , that is something less than 2 to 1. Thus any Numb . of Throws may be easily found , but the following Proposition will shew you a more compendious way of Calculation . PROP. XI . To find at how many times one may undertake to throw 12 with Two Dice . IF one should undertake it at One Throw , it 's clear he has but one Chance to get the Stake a , and 35 to get nothing ; so , by the Second Proposition , he has much 1 / 36 a. He who undertakes to do it at Twice , if he throw 12 the first time gains a , if otherwise , then there remains to him One Throw , which , by the former Case , is worth 1 / 36 a ; but there is but One Chance which gives 12 at the first Throw , and 35 Chances against him ; so he has 1 Chance for a , and 35 for 1 / 36 a , which , by the Second Proposition , is worth 71 / 1296 a , and there remains to his Fellow-Gamester 1●2● / 1296 a. From these it's easie to find the Value of his Hazard , who undertakes it at four times ; passing by his Case who undertakes it at three times . If he who undertakes to do it at four times throws 12 the first or second Cast , then he has a , if not , there remains two other Throws , which , by the former Case , are worth 71 / 1296 a ; but for the same reason , in his two first Throws , he has 71 Chances which give him a , against 1225 Chances , in which it may happen otherwise ; therefore at first he has 71 Chances which give him a , and 1225 which give him 71 / 1296 a , which , by the Second Proposition , is worth 19006●5 / 167961● a , which shews that their Hazards to one another are as 178991 to 1500625. From which Cases it is easie to find the Value of his Expectation , who undertakes to do it at 8 times , and from that , his Case who undertakes to do it at 16 times ; and from his Case who undertakes to do it at 8 times ; and his likewise who undertakes to do it at 16 times ; it is easie to determin his Expectation who undertakes it at 24 times : In which Operation , because that which is principally sought , is the Number of Throws , which makes the Hazard equal on both sides , viz. to him who undertakes , and he who offers , you may , without any sensible Error , from the Numbers ( which else would grow very great ) cut off some of the last Figures . And so I find , that he who undertakes to throw 12 with Two Dice , at 24 times , has some Loss , and he who undertakes it at 25 times , has some Advantage . PROP. XII . To find with how many Dice , one can undertake to throw two Sixes at the first Cast. THis is as much , as if one would know , at how many Throws of one Dye , he may undertake to throw twice Six ; now if any should undertake it at two Throws , by what we have shewn before , his Hazard would be 1 / 36 a , he who would undertake to do it at 3 ; times , if his first Throw were not 6 , then there would remain two Throws , each of which must be 6 , which ( as we have said ) is worth 1 / 36 a ; but if the first Throw be 6 , he wants only one 6 in the two following Throws , which by the Tenth Proposition , is worth 11 / 36 a ; but since he has but one Chance to get 6 the first Throw , and five to miss it ; he has therefore , at first , one Chance for 11 / 36 a , and five Chances for 1 / 36 a , which , by the Second Proposition , is worth 16 / 216 a , or 2 / 27 a , after this manner still assuming 1 Chance more , you will find that you may undertake to throw two Sixes at 10 Throws of one Dye , or 1 Throw of ten Dice , and that with some Advantage . PROP. XIII . If I am to play with another One Throw , on this condition , that if 7 comes up I gain , if 10 he gains ; if it happens that we must divide the Stake , and not play , to find how much belongs to me , and how much to him . BEcause of the 36 different Throws of the Two Dice , there are six which give 7 and 3 , which give 10 and 27 , which equals the Game , in which Case there is due to each of us ½ a : But if none of the 27 should happen , I have 6 , by which I may gain a , and 3 , by which I may get nothing , which , by the Second Proposition , is worth ⅔ a ; so I have 27 Chances for ½ a , and 9 for ⅔ a , which , by the second Proposition , is worth 13 / 24 a , and there remains to my Fellow-Gamester 11 / 24 a. PROP. XIV . If I were playing with another by turns , with two Dice , on this condition , that if I throw 7 I gain , and if he throw 6 he gains , allowing him the first Throw : To find the proportion of my Hazard to his . SUppose I call the Value of my Hazard x , and the Stakes a , then his Hazard will be a − x ; then whenever it 's his turn to throw , my Hazard is x , but when it 's mine , the Value of my Hazard is greater . Suppose I then call it y ; now because of the 36 Throws of Two Dice , there are five which give my Fellow-Gamester 6 , thirty one which bring it again to my turn to throw , I have five Chances for nothing , and thirty one for y , which , by the Third Proposition , is worth 31 / 36 y ; but I suppos'd at first my Hazard to be x ; therefore 31 / 36 y = x , and consequently y = 36 / 3●x . I suppos'd likewise , when it was my turn to throw , the Value of my Hazard was y , but then I have six Chances which give me 7 , and consequently the Stake , and thirty which give my Fellow the Dice , that is , make my Hazard worth x ; so I have six Chances for a , and thirty for x , which , by Prop. 3. is worth but this by supposition is equal to y , which is equal ( by what has been prov'd already ) to 36 / 3● x ; therefore , and consequently x = 31 / 6●a , the Value of my Hazard , and that of my Fellow-Gamester is 30 / 61 a ; so that mine is to his as 31 to 30. Here follow some Questions which serve to exercise the former Rules . 1. A and B play together with two Dice , A wins if he throws 6 , and B if he throws 7 ; A at first gets one Throw , then B two , then A two , and so on by turns , till one of them wins . I require the proportion of A's Hazard to B's ? Answer , It is as 10355 to 12276. 2. Three Gamesters , A , B , and C , take 12 Counters , of which there are four white and eight black ; the Law of the Game is this , that he shall win , who , hood-wink'd , shall first chuse a white Counter , and that A shall have the first choice , B the second , and C the third , and so , by turns , till one of them win . Quaer . What is the proportion of their Hazards ? 3. A wagers with B , that of 40 Cards , that is , 10 of every Suit , he will pick out four ; so that there shall be one of every suit ; A's Hazard to B's , in this Case , is as 1000 to 8139. 4. Supposing , as before , 4 white Counters and 8 black , A wagers with B , that out of them , he shall pick 7 Counters , of which there are 3 white . I require the proportion of A's Hazard to B's ? 5. A and B taking 12 Counters , play with three Dice after this manner ; that if 12 comes up , A shall give one Counter to B , but if 14 comes up , B shall give one to A , and that he shall gain who first has all the Counters . A's Hazard to B's is 244140625 to 282429 536481. The Calculus of the preceeding Problems is left out by Mons. Hugens , on purpose that the ingenious Reader may have the satisfaction of applying the former Method himself ; it is in most of them more laborious than difficult ; for Example , I have pitch'd upon the Second and Third , because the rest can be solv'd after the same Method . Problem 1. The first Problem is solv'd by the Method of Prop. 14. only with this difference , that after you have found the share due to B , if A were to get no first Throw , you must subtract from it 5 / 36 of the Stake which is due to A for his Hazard of throwing Six at the first Throw . Probl. 2 As for the second Problem , it is solved thus , Suppose A's Hazard , when it is his own turn to chuse , be x , when it is B's , be y , and when it is C's , be z ; it is evident , when out of 12 Counters , of which there are 4 white and 8 black , he endeavours to chuse a white one , he has four Chances to get it , and eight to miss it , that is , he has four Chances to get the Stake a , and eight to make his Hazard worth y ; so , and consequently . When it is B's turn to chuse , then he has four Chances for nothing , and eight for z , ( that is to bring it to C's turn ) consequently ; this equation reduc'd gives ; when it comes to C's turn to chuse then A has four Chances for nothing , and eight for x , consequently z = 8 / 12x , therefore ; this equation reduc'd gives x = 9 / 19a , and consequently there remains to the B and C 10 / 19 a , which must be shar'd after the same manner , that is , so that B have the first Choice , C the next , and so on , till one of them gain ; the reason is , because it had been just in A to have demanded 9 / 19 of the Stake for not playing , and then the seniority fell to B ; now 10 / 19 a parted betwixt B and C , by the former method , gives 6 / 19 to B , and 4 / 19 to C ; so A , B , and C's Hazards , from the beginning , were as 9 , 6 , 4. I have suppos'd here the sense of the Problem to be , that when any one chus'd a Counter , he did not diminish their Number ; but if he miss'd of a white one , put it in again , and left an equal Hazard to him who had the following Choice ; for if it be otherwise suppos'd , A's share will be 55 / 123 , which is less than 9 / 19. Prob. 2. It is evident , that wagering to pick out 4 Cards out of 40 , so that there be one of every Suit , is no more , than wagering , out of 39 Cards to take 3 which shall be of three proposed Suits ; for it is all one which Card you draw first , all the Hazard being , whether out of the 39 remaining you take 3 , of which none shall be of the Suit you first drew . Suppose then you had gone right for three times , and were to draw your last Card , it is clear , that there are ●7 Cards , ( viz. of the Suits you have drawn before ) of which , if you draw any you lose , and 10 of which , if you draw any , you have the Stake a ; so you have 10 Chances for a , and 27 for nothing , which , by Prop. 3. is worth 10 / 37 a. Suppose again you had gone right only for two Draughts , then you have 18 Cards ( of the Suits you have drawn before ) which make you lose , and 20 , which put you in the Case suppos'd formerly , viz. where you have but one Card to draw , which , as we have already calculated , is worth 10 / 37 a ; so you have 18 Chances for nothing , and 20 for 10 / 37 a , which , by Prop. 3. is worth 100 / 703 a. Suppose again you have 3 Cards to draw , then you have 9 ( of the Suit you drew first ) which make you lose , and 30 which put you in the Case suppos'd last ; so you have 9 Chances for nothing , and 30 for 100 / 703 a , which , by Prop. 3. is worth 3000 / 27417 a , or 1000 / 9139 a , and you leave to your Fellow-Gamester 8139 / 9139 a ; so your Hazard is to his as 1000 to 8139. It is easie to apply this Method to the Games that are in use amongst us : For Example , If A and B , playing at Backgammon , B had already gain'd one end of three , and A none , and if A had the Dice in his Hand for the last Throw of the second end , all his Men but two upon the Ace Point being already cast of : Quaer . What is the proportion of As Hazard to Bs ? Solution : There being of the 36 Throws of two Dice , six which give Doublets ; if A throw any of the Six , he has the Stake a ; if he throw any of the other Thirty , then he wants but one Game , and his Fellow-Gamester three , which , by Prop. V. is worth ⅞ a ; so A has six Chances for a , and thirty for ⅞ a , which , by Prop. 3. is worth 129 / 144 a , and there remains to his Play-Fellow 15 / 144 a ; so A's Hazard to B's , is as 129 to 15 , that is , less than 9 to 1. Supposing the same Case , and if their Bargain had been , that he who gain'd three ends before the other gain'd one , should have double of what each stak'd , that is , the Stake and a half more , then there had been due to A 282 / 285 of the Stake , that is , B ought only to take 1 / ●● , and leave the rest to A. Thus likewise , if you apply the former Rule to the Royal Oak-Lottery , you will find , that he who wagers that any Figure shall come up at the first throw , ought to wagers 1 against 31 ; that he who wagers it shall come up at one of two throws , ought to wager 63 against 961 ; that he who wagers that a Figure shall come up at once in three times , ought to lay 124955 against 923621 , &c. it being only somewhat tedious to calculate the rest . Where you will find , that the equality will not fall as some imagin on 16 Throws , no more than the equality of wagering at how many Throws of one Dye 6 shall come up , falls on three ; the contrary of which you have seen already demonstrated ; you will find by calculation , that he has the Disadvantage , who wagers , that 1 of the 32 different Throws of the Royal Oak-Lottery , shall come at once of 20 times , and that he has some Advantage , who wagers on 22 times ; so the nearest to Equality is on 21 times : But it must be remembred , that I have suppos'd in the former Calculation , the Ball in the Royal Oak-Lottery to be regular , tho it can never be exactly so ; for he who has the smallest Skill in Geometry , knows , that there can be no regular Body of 32 sides , and yet this can be of no advantàge to him who keeps it . To find the Value of the Throws of Dice as to the Quantity . NOthing is more easie , than by the former Method to determine the Value of any Number of Throws of any Number of Dice ; for in one Throw of a Dye , I have an equal chance for 1 , 2 , 3 , 4 , 5 , 6 , consequently my Hazard is worth their Sum 21 divided by their Number 6 , that is , 3½ . Now if one Throw of a Dye be worth 3½ , then two Throws of a Dye , or one Throw of two Dice is worth 7 , two Throws of two Dice , or one Throw of four Dice is worth 14 , &c. The general Rule being to multiply the Number of Dice , the Number of Throws , and 3½ continually . This is not to be understood as if it were an equal Wager to throw 7 , or above it , with two Dice at one Throw ; for he who undertakes to do so , has the advantage by 21 against 15. The meaning is only , if I were to have a Guinea , a Shilling , or any thing else , for every Point that I threw with two Dice at one Throw , my Hazard is worth 7 of these , because he who gave me 7 for it , would have an equal probability of gaining or losing by it , the Chances of the Throws above 7 being as many , as of these below it : So it is more than an equal Wager to throw 14 at least at two Throws of two Dice , because it is more probable that 14 will come , than any one Number besides , and as probable that it will be above it as below it ; but if one were to buy this Hazard at the rate above-mention'd , he ought just to give 14 for it . The equal Wager in one Throw of two Dice , is to throw 7 at least one time , and 8 at least another time , and so per vices : The reason is , because in the first Case I have 21 Chances against 15 , and in the second 15 Chances against 21. Of RAFFLING . IN Raiffing the different throws and their Chances are these ; Where it is to be observed , that of the 216 different Throws of three Dice , there are only 96 that give Doublets , or two , at least , of a kind ; so it is 4 to 5 that with three Dice Throws . Chan. 3 18 1 4 17 3 5 16 6 6 15 4 7 14 9 8 13 9 9 12 7 10 11 9 you shall throw Doublets , and it is 1 to 35 that you throw a Raffle , or all three of a kind . It is evident likewise , that it is an even Wager to throw 11 or above it , because there are as many Chances for 11 , and the Throws above it , as for the Throws below it ; but tho it be an even Wager to throw 11 at one Throw , it is a disadvantage to wager to throw 22 at two Throws , and far more to wager to throw 33 at three Throws ; and yet it is more than an equal Wager that you shall throw 21 at two Throws in Raffling , because it is as probable that you will , as that you will not throw 11 , at least , the first time , and more than probable that you will throw 10 , at least , the second time . For an instance of the plainness of the preceeding Method , I will shew , how by simple Subtraction , the most part of the former Problems may be solv'd . Suppose A and B , playing together , each of 'em stakes 32 Shillings , and that A wants one Game of the Number agreed on , and B wants two ; to find the share of the Stakes due to each of ' em . It 's plain , if A wins the next Game he has the whole 64 Shillings ; if B wins it , then their Shares are equal ; therefore says A to B , If you will break off the Game , give me 32 , which I am sure of , whether I win or lose the next Game , and since you will not venture for the other 32 , let us part them equally , that is , give me 16 , which , with the former 32 , make 48 , leaving 16 to you . Suppose A wanted one Game , and B three ; if A wins the next Game , he has the 64 Shillings ; if B wins it , then they are in the condition formerly suppos'd , in which Case there is 48 due to A ; therefore says A to B , give me the 48 which I am sure of , whether I win or lose the next Game , and since you will not hazard for the other 16 , let us part them equally , that is , give me 8 , which , with the former 48 , make 56 , leaving 8 to you , and so all the other Cases may be solv'd after the same manner . Suppose A wagers with B , that with one Dye he shall throw 6 at one of three Throws , and that each of them stakes 108 Guineas : To find what is the proportion of their Hazards ; Now there being in one Throw of a Dye but one Chance for 6 , and five Chances against it , one Throw for 6 is worth 1 / 6 of the Stake ; therefore says B to A , of the 216 Guineas take a sixth part for your first Throw , that is , 36 ; for your next Throw take a sixth part of the remaining 180 , that is , 30 ; and for your third Throw , take a sixth part of the remaining 150 , that is , 25 , which in all make 91 , leaving to me 125 ; so his Hazard who undertakes to throw 6 at one of three Throws , is 91 to 125. Suppose A had undertaken to throw 6 with one Dye at one Throw of four , and that the whole Stake is 1296 ; says A to B , Every Throw for 6 of one Dye , is worth the sixth part of what I throw for ; therefore for my first Throw give me 216 , which is the sixth part of 1296 , and there remains 1080 , I must have the sixth part of that , viz. 180 , for my second Throw ; and the sixth part of the remaining 900 , which is 150 , for my third Throw ; and the sixth part of the last remainder 750 , which is 125 for my fourth Throw ; all this added together makes 671 , and there remains to you 625 ; so it is evident , that A's Hazard , in this Case , is to B's 671 to 625. Suppose A is to win the Stakes ( which we shall suppose to be 36 ) if he throws 7 at once of twice with two Dice , and B is to have them if he does not ; says B to A , the Chances which give 7 are 6 of the 36 , which is as ' much as 1 of 6 ; therefore for your first Throw you shall have a sixth part of the 36 , which is 6 ; and for your next Throw a sixth part of the remainder 30 , which is 5 ; this in all makes 11 ; so you leave 25 to me ; so A's Hazard is to B's as 11 to 25. It were easie , at this rate to calculate the most intricate Hazards , were it not that Fractions will occur , which , if they be more than ½ , may be suppos'd equal to an Unit , without causing any remarkable Error in great Numbers . It will not be amiss , before I conclude , to give you a Rule for finding in any Number of Games the Value of the first , because Hugens's Method , in that Case , is something tedious . Suppose A and B had agreed , that he should have the Stakes who did win the first 9 Games , and A had already won one of the 9 ; I would know what share of B's Mony is due to A for the Advantage of this Game . To find this , take the first eight even Numbers 2 , 4 , 6 , 8 , 10 , 12 , 14 , 16 , and multiply them continually ; that is , the first by the second , the product by the third , &c. take the first eight odd Numbers , 1 , 3 , 5 , 7 , 9 , 11 , 13 , 15 , and do just so by them , the product of the even Number is the Denominator , and the product of the odd Number the Numerator of a Fraction , which expresseth the quantity of B's Money due to A upon the winning of the first Game of 9 ; that is , if each stak'd a number of Guineas , or Shillings , &c. express'd by the product of the even Numbers , there would belong to A , of B's Money , the Number express'd by the product of the odd Numbers : For Example , Suppose A had gain'd one Game of 4 , then by this Rule , I take the three first even Numbers , 2 , 4 , 6 , and multiply them continually , which make 48 , and the first three odd Numbers , 1 , 3 , 5 , and multiply them continually , which make 15 ; so there belongs to A 15 / 48 of B's Money , that is , if each stak'd 48 , there would belong to A , besides his own 15 of A's . Now by Hugens's Method , if A wants but three Games while B wants four , there is due to A 21 / 32 of the Stake ; by this Rule there is due to A 15 / 48 of B's Money , which is 15 / 69 of the Stake , which , with his own 48 / 96 of the Stake , makes 63 / 96 or 21 / 32 of the Stake , and so in every Case you will find Hugens's Method and this will give you the same Number ; a Demonstration of it you may see in a Letter of Monsieur Pascals to Monsieur Fermat ; tho it be otherwise express'd there than here , yet the consequence is easily supply'd . To prevent the labour of Calculation , I have subjoyn'd the following Table , which is calculated for two Gamesters , as Mons. Hugens is for three . If each of us stake 256 Guineas in There belongs to me of 256 of my Play-fellow The Use of the Table is plain ; for let our Stakes be what they will , I can find the Portion due to me upon the winning the first , or the first two Games , &c. of 2 , 3 , 4 , 5 , 6. For Example , If each of us had stak'd 4 Guineas , and the Number of Games to be plaid were 3 , of which I had gain'd 1 , say , As 256 is to 96 , so is 4 to a fourth . 256 : 96 : : 4 : 1½ To find what is the Value of his Hazard , who undertakes , at the first Throw , to cast Doublets , in any given Number of Dice . In two Dice it is plain to avoid Doublets , every one of the six different Throws of the first , can only be combin'd with five of the second , because one of the six is of the same kind , and consequently makes Doublets ; for the samo reason , the thirty Throws of two Dice , which are not Doublets , can only be combin'd with four Throws of a third Dice , and three Throws of a fourth Dice ; so generally it is this Series , 6 × 5 × 4 × 3 × 2 × 1 × 0 , &c. 6 × 6 × 6 × 6 × 6 × 6 × 6 , &c. The second Series is the Sum of the Chances , and the first the Number of Chances against him who undertakes to throw Doublets , each Series to be continu'd so many terms , as are the Number of Dice . For Example , If one should undertake to throw Doublets at the first Throw of four Dice , his Adversary's Hazard is or 5 / 18 leaving to him 13 / 18 , so he has 13 to 5. In seven Dice , you see the Chances against him are o , because then there must necessarily be Doublets . Of WHIST . IF there be four playing at Whist , it is 15 to 1 that any two of them shall not have the four Honours , which I demonstrate thus : Suppose the four Gamesters be A , B , C , D : If A and B had , while the Cards are a dealing , already got three Honours , and wanted only one , since it is as probable that C and D will have the next Honour , as A and B ; if A and B had laid a Wager to have it , there is due to them but ½ of the Stake : If A and B wanted two of the four , and had wager'd to have both those two , then they have an equal Hazard to get nothing ; if they miss the first of those two , or to put themselves in the former Case if they get it ; so they have an equal Hazard to get nothing or ½ , which , by Prop. 1. is worth ¼ of the Stake ; so if they want three Honours , you will find due to them 1 / 8 of the Stake ; and if they wanted four , 1 / 16 of the Stake , leaving to C and D 15 / 16 ; so C and D can wager 15 to 1 , that A and B shall not have all the four Honours . It is 11 to 5 that A and B shall not have three of the four Honours , which 1 prove thus : It is an even Wager , if there were but three Honours , that A and B shall have two of these three , since 't is as probable that they will have two of the three , as that C and D shall have them ; consequently , if A and B had laid a Wager to have two of three , there is due to them ½ of the Stake . Now suppose A and B had wager'd to have three of four , they have an equal Hazard to get the first of the four , or miss it ; if they get it , then they want two of the three , and consequently there is due to them ½ of the Stake ; if they miss it , then they want three of the three , and consequently there is due to them 1 / 8 of the Stake ; therefore , by Prop. 1. their Hazard is worth 5 / 16 , leaving to C and D 11 / 16. A and B playing at Whist against C and D ; A and B have eight of ten , and C and D nine , and therefore can't reckon Honors ; to find the proportion of their Hazards . There is 5 / 16 due to C and D upon their hazard of having three of four Honours ; but since A and B want but one Game , and C and D two , there is due to C and D but ¼ , or 4 / 16 more upon that account , by Prop. 4. this in all makes 9 / 16 , leaving to A and B 7 / 16 ; so the hazard of A and B to that of C and D , is as 9 to 7. In the former Calculations I have abstracted from the small difference of having the Deal and being Seniors . All the former Cases can be calculated by the Theorems laid down by Monsieur Hugens ; but Cases more compos'd require other Principles , for the easie and ready Computation of which , I shall add one Theorem more , demonstrated after Mons. Hugens's Method . Theor. If I have p Chances for a , q Chances for b , and r Chances for c , then my hazard is worth , that is , a multiplied into the number of its Chances added to b , multiplied into the number of its Chances , added to c multiplied into the number of its Chances , and the Sum divided by the Sum of Chances of a , b , c. To investigate as well as demonstrate this Theorem , suppose the value of my hazard be x , then x must be such , as having it , I am able to purchase as good a hazard again in a just and equal Game . Suppose the Law of it be this , That playing with so many Gamesters as , with my self , make up the number p+q+r , with as many of them as the nnmber p represents ; I make this bargain , that whoever of them wins shall give me a , and that I shall do so to each of them if I win ; with the Gamesters represented by the number of q , I bargain to get b , if any of them win , ann to give b to each of them , if I win my self ; and with the rest of the Gamesters , whose number is r − 1 , I bargain to give , or to get c after the same manner : Now all being in an equal probability to gain , I have p Chances to get a , q Chances to get b , and r − 1 Chances to get c , and one Chance , viz. when I win my self , to get px+qx+rx − ap − bq − rc+c , which , if it be suppos'd equal to c , then I have p Chances for a , q Chances for b , and r Chances for c ( for I had just now r − 1 Chances for it ) therefore , if px+qx+rx − ap − bq − rc+c = c , then is . By the same way of reasoning you will find , if I have p Chances for a , q Chances for b , r Chances for c , and s Chances for d , that my hazard is , &c. In Numbers . If I had two Chances for 3 Shillings , four Chances for 5 Shillings , and one Chance for 9 Shillings , then , by this Rule , my hazard is worth 5 Shillings ; for ; and it is easie to prove , that with 5 Shillings I can purchase the like hazard again ; for suppose I play with six others , each of us staking 5 Shillings ; with two of them I bargain , that if either of them win , he must give me 3 Shillings , and that I shall do so to them ; and with the other four I bargain just so , to give or to get 5 Shillings : This is a just Game , and all being in an equal probability to win ; by this means I have two Chances to get 3 Shillings , four Chances to get 5 Shillings , and one Chance to get 9 Shillings , viz. when I win my self ; for then out of the Stake , which makes 35 Shillings , I must give the first two 6 Shillings , and the other four 20 Shillings , so there remains just 9 to my self . It it easie , by the help of this Theorem , to calculate in the Game of Dice , commonly call'd Hazard , what Mains are best to sett on , and who has the Advantage , the Caster or Setter . The Scheme of the Game , as I take it , is thus ,   Throws next following for Mains . The Caster . The Setter . V. V. II. III. XI . XII . VI. VI. XII . XI . II. III. VII . VII . XI . XII . II. III. VIII . VIII . XII . XI . II. III. IX . IX . II. III. XI . XII . By an easie Calculation you will find , if the Caster has VI. and the Setter VII , there is due to the Caster ⅓ of the Stake ; if he has V. against VII . 2 / 5 of the Stake , VI. against VII . 5 / 11 of the Stake , IV. against VI. 3 / 8 of the Stake , V. against VI. 4 / 9 of the Stake , VI. against V. 3 / 7 of the Stake , I need not tell the Reader , that IV. is the same with X , V. with IX , and VI. with VIII . Suppose then VII . be the Main : To find the proportion of the hazard of the Caster to that of the Setter . By the Law of the Game , the Caster , before he throws next , has four Chances for nothing , viz. these II , III , XII ; eight Chances for the whole Stake , viz. those of VII , XI ; six Chances for ⅓ , viz. those IV , X ; eight Chances for 2 / 5 , viz. those of V , IX ; and ten Chances for 5 / 11 , viz. these of VI , X ; so his hazard , by the preceding Theorem , is Now to save the trouble of a tedious reduction , Suppose the Stake which they play for be 36 , that is , the Setter had laid down 18 ; in that case , every one of these Fractions are so many parts of an Unite , which , being gather'd into one Sum , give 1741 / 59 to the Caster , leaving 1814 / 55 to the Setter ; so the hazard of the Caster is to that of the Setter 244 , 251. Suppose VI. or VIII . be the Main , then the Share of the Caster is II. III. VI. IV. V. XI . XII . X. IX . VIII . VII . 5×0+6×1+6×3 / 8+8×4 / 9+5×½+6×6 / 11 = = 17229 / 396 , leaving to the Setter 18167 / 396 , so the hazard of the Caster is to that of the Setter as 6961 to 7295. Suppose V. or IX . be the Main , then the Share of the Caster is II. III. XI . IV. VI. XII . V. X. IX . VIII . VII . 6×0+4×1+6×●+4×½+10×●+6×● = = 17 229 / 315 , leaving to the Setter is 1886 / 315 , so the hazard of the Caster is to that of the Setter as 1396 to 1493. It is plain , that in every Case the Caster has the Disadvantage , and that V. or IX . are better Mains to set on than VII , because , in this last Cast the Setter has but 18 and 14 / 55 or 84 / 330 ; whereas , when V. or IX . is the Main , he has 1886 / 315 ; likewise VI. or VIII . are better Mains than V. or IX . because 167 / 396 is a greater Froction than 86 / 315. All those Problems suppose Chances , which are in an equal probability to happen , if it should be suppos'd otherwise , there will arise variety of Cases of a quite different nature , which , perhaps , 't were not unpleasant to consider , I shall add one Problem of that kind , leaving the Solution to those who think it merits their pains . In Parallelipipedo cujus latera sunt ad invicem in ratione a , b , c : Invenire quotâ vice quivis suscipere potest , ut datum quodvis planum , v. g. ab jaciat . FINIS . ERRATA . PReface , page 3. line 1. read in . p. 6. l. 5. r. incur . p. 10. l. 8. for is left to me , r. properly deserves the name of Conduct . Book , p. 2. l. 7. for 9 r. q. p. 16. l. 5. add and he one . p. 71. l. 5. r. wins . Advertisement . THe whole Duty of Man according to the Law of Nature . By that famous Civilian SAMUEL PUFFENDORF , Professor of The Law of Nature and Nations , in the University of Heidelberg , and in the Caroline University , afterwards Counsellour and Historiographer to the K. of Sweden , and to his Electoral Highness of Brandenburg . Now made English. Printed for C. Harper , at the Flower-de-Luce over-against St. Dunstan's Church in Fleetstreet .