Dice rolling probability game












4












$begingroup$


In a hockey-themed board game, players start the game in the penalty box. If rolling the same number on both dice is required to escape from the penalty box, and Piper, Quincy, and Riley take turns, in he order named, rolling a pair of standard six sided dice, what is the probability that Piper is the last player to escape from the penalty box?





My initial thought was that riley and quincy both escape with a 1/36 probability. So, we multiply the three together getting $frac{1}{36^3}$, but this is clearly incorrect.



Then I took more thinking to this problem. To satisfy the problem we need Piper to lose her first throw, Quincy to win her throw, Riley to win her throw, then Piper will eventually win her throw. So we have $dfrac{5}{6} cdot dfrac{1}{6} cdot dfrac{1}{6} cdot = dfrac{5}{6^{3}}$.



However, there other cases where Piper looses, Quincy looses, Riley looses, Piper looses, then Quincy and Riley wins, or where Riley wins before Quincy.



So this can account into what I'm thinking of an infinitely long geometric sequence that later converges to a rational number.



There are many, many more cases. To account for this, I have to keep analyzing all possibilities at each turn, and I believe that eventually I will get some geometric progressions. However, this seems tedious and error prone.



So then I thought that I could just denote the probabilities that I am interested in by letters and write some equations. For instance, if the probability of Piper escaping last is $p$, then after a turn in which nobody escapes the probability of Piper escaping last is still $p$.



This allows me to write the equation: $$p= {5over 6}^3cdot p +text{other cases }.$$



But however, I cannot seem to find that "other cases" thing, and I even further doubted that the $p$ in the equation is stable.



But after some further examination, I find this is not so. I considered first the case with two players: Let $p$ be the probability that the player who starts first escapes first and $q$ the probability that the second player escapes first. I could write the equation $p=1/6+5/6cdot q$ because the probability of the first player escaping is 1/6 plus the probability of him not escaping (5/6) times the probability of him winning as second player, because now the other player rolls the dice first.



Another equation I could write is $p+q=1$ because one of them will escape eventually (with probability 1). Solving this I get $p=1/6+5/6(1-p)$ etc. which leads to $p=6/11$. This is incorrect.



And, after a long time of thoughts, I finally figured the way to write the infinite sum, $p=1/6 + (5/6)^2cdot 1/6+(5/6)^4cdot 1/6+dots$, because the probability of the first player escaping first is 1/6 (if he rolls a double) + (5/6)^2 (=probability of both not rolling a double) times 1/6 (rolling a double at the second turn) and so on...



The sum of that infinite progression is $$p=1/6cdot {1over 1-(5/6)^2}$$ which still gives $6/11$, and is wrong again.



I cannot think of a way to continue. Help please?










share|cite|improve this question









$endgroup$








  • 1




    $begingroup$
    Why do you think $frac6{11}$ is an incorrect answer to the two-player question?
    $endgroup$
    – David K
    1 hour ago










  • $begingroup$
    @DavidK because its not the right answer in relation to the answer key.
    $endgroup$
    – Max0815
    58 mins ago










  • $begingroup$
    You started out working on a problem with three players. If there is an answer key, I would expect it to answer that question. It seems you came up with the two-player problem on your own; how could the answer key anticipate that and give the answer to a question that isn't in the original materials?
    $endgroup$
    – David K
    56 mins ago










  • $begingroup$
    @DavidK Wait I misread your question. There is an answer to the three player one, and I thought you meant that. I was experimenting with the two player one and one of aops' answerers said that it was not right.
    $endgroup$
    – Max0815
    53 mins ago












  • $begingroup$
    You were determining the probability that Piper gets out first, not last. The probability that she gets out last in the two-player game (if she goes first) is $frac{5}{11}$.
    $endgroup$
    – Robert Shore
    50 mins ago


















4












$begingroup$


In a hockey-themed board game, players start the game in the penalty box. If rolling the same number on both dice is required to escape from the penalty box, and Piper, Quincy, and Riley take turns, in he order named, rolling a pair of standard six sided dice, what is the probability that Piper is the last player to escape from the penalty box?





My initial thought was that riley and quincy both escape with a 1/36 probability. So, we multiply the three together getting $frac{1}{36^3}$, but this is clearly incorrect.



Then I took more thinking to this problem. To satisfy the problem we need Piper to lose her first throw, Quincy to win her throw, Riley to win her throw, then Piper will eventually win her throw. So we have $dfrac{5}{6} cdot dfrac{1}{6} cdot dfrac{1}{6} cdot = dfrac{5}{6^{3}}$.



However, there other cases where Piper looses, Quincy looses, Riley looses, Piper looses, then Quincy and Riley wins, or where Riley wins before Quincy.



So this can account into what I'm thinking of an infinitely long geometric sequence that later converges to a rational number.



There are many, many more cases. To account for this, I have to keep analyzing all possibilities at each turn, and I believe that eventually I will get some geometric progressions. However, this seems tedious and error prone.



So then I thought that I could just denote the probabilities that I am interested in by letters and write some equations. For instance, if the probability of Piper escaping last is $p$, then after a turn in which nobody escapes the probability of Piper escaping last is still $p$.



This allows me to write the equation: $$p= {5over 6}^3cdot p +text{other cases }.$$



But however, I cannot seem to find that "other cases" thing, and I even further doubted that the $p$ in the equation is stable.



But after some further examination, I find this is not so. I considered first the case with two players: Let $p$ be the probability that the player who starts first escapes first and $q$ the probability that the second player escapes first. I could write the equation $p=1/6+5/6cdot q$ because the probability of the first player escaping is 1/6 plus the probability of him not escaping (5/6) times the probability of him winning as second player, because now the other player rolls the dice first.



Another equation I could write is $p+q=1$ because one of them will escape eventually (with probability 1). Solving this I get $p=1/6+5/6(1-p)$ etc. which leads to $p=6/11$. This is incorrect.



And, after a long time of thoughts, I finally figured the way to write the infinite sum, $p=1/6 + (5/6)^2cdot 1/6+(5/6)^4cdot 1/6+dots$, because the probability of the first player escaping first is 1/6 (if he rolls a double) + (5/6)^2 (=probability of both not rolling a double) times 1/6 (rolling a double at the second turn) and so on...



The sum of that infinite progression is $$p=1/6cdot {1over 1-(5/6)^2}$$ which still gives $6/11$, and is wrong again.



I cannot think of a way to continue. Help please?










share|cite|improve this question









$endgroup$








  • 1




    $begingroup$
    Why do you think $frac6{11}$ is an incorrect answer to the two-player question?
    $endgroup$
    – David K
    1 hour ago










  • $begingroup$
    @DavidK because its not the right answer in relation to the answer key.
    $endgroup$
    – Max0815
    58 mins ago










  • $begingroup$
    You started out working on a problem with three players. If there is an answer key, I would expect it to answer that question. It seems you came up with the two-player problem on your own; how could the answer key anticipate that and give the answer to a question that isn't in the original materials?
    $endgroup$
    – David K
    56 mins ago










  • $begingroup$
    @DavidK Wait I misread your question. There is an answer to the three player one, and I thought you meant that. I was experimenting with the two player one and one of aops' answerers said that it was not right.
    $endgroup$
    – Max0815
    53 mins ago












  • $begingroup$
    You were determining the probability that Piper gets out first, not last. The probability that she gets out last in the two-player game (if she goes first) is $frac{5}{11}$.
    $endgroup$
    – Robert Shore
    50 mins ago
















4












4








4





$begingroup$


In a hockey-themed board game, players start the game in the penalty box. If rolling the same number on both dice is required to escape from the penalty box, and Piper, Quincy, and Riley take turns, in he order named, rolling a pair of standard six sided dice, what is the probability that Piper is the last player to escape from the penalty box?





My initial thought was that riley and quincy both escape with a 1/36 probability. So, we multiply the three together getting $frac{1}{36^3}$, but this is clearly incorrect.



Then I took more thinking to this problem. To satisfy the problem we need Piper to lose her first throw, Quincy to win her throw, Riley to win her throw, then Piper will eventually win her throw. So we have $dfrac{5}{6} cdot dfrac{1}{6} cdot dfrac{1}{6} cdot = dfrac{5}{6^{3}}$.



However, there other cases where Piper looses, Quincy looses, Riley looses, Piper looses, then Quincy and Riley wins, or where Riley wins before Quincy.



So this can account into what I'm thinking of an infinitely long geometric sequence that later converges to a rational number.



There are many, many more cases. To account for this, I have to keep analyzing all possibilities at each turn, and I believe that eventually I will get some geometric progressions. However, this seems tedious and error prone.



So then I thought that I could just denote the probabilities that I am interested in by letters and write some equations. For instance, if the probability of Piper escaping last is $p$, then after a turn in which nobody escapes the probability of Piper escaping last is still $p$.



This allows me to write the equation: $$p= {5over 6}^3cdot p +text{other cases }.$$



But however, I cannot seem to find that "other cases" thing, and I even further doubted that the $p$ in the equation is stable.



But after some further examination, I find this is not so. I considered first the case with two players: Let $p$ be the probability that the player who starts first escapes first and $q$ the probability that the second player escapes first. I could write the equation $p=1/6+5/6cdot q$ because the probability of the first player escaping is 1/6 plus the probability of him not escaping (5/6) times the probability of him winning as second player, because now the other player rolls the dice first.



Another equation I could write is $p+q=1$ because one of them will escape eventually (with probability 1). Solving this I get $p=1/6+5/6(1-p)$ etc. which leads to $p=6/11$. This is incorrect.



And, after a long time of thoughts, I finally figured the way to write the infinite sum, $p=1/6 + (5/6)^2cdot 1/6+(5/6)^4cdot 1/6+dots$, because the probability of the first player escaping first is 1/6 (if he rolls a double) + (5/6)^2 (=probability of both not rolling a double) times 1/6 (rolling a double at the second turn) and so on...



The sum of that infinite progression is $$p=1/6cdot {1over 1-(5/6)^2}$$ which still gives $6/11$, and is wrong again.



I cannot think of a way to continue. Help please?










share|cite|improve this question









$endgroup$




In a hockey-themed board game, players start the game in the penalty box. If rolling the same number on both dice is required to escape from the penalty box, and Piper, Quincy, and Riley take turns, in he order named, rolling a pair of standard six sided dice, what is the probability that Piper is the last player to escape from the penalty box?





My initial thought was that riley and quincy both escape with a 1/36 probability. So, we multiply the three together getting $frac{1}{36^3}$, but this is clearly incorrect.



Then I took more thinking to this problem. To satisfy the problem we need Piper to lose her first throw, Quincy to win her throw, Riley to win her throw, then Piper will eventually win her throw. So we have $dfrac{5}{6} cdot dfrac{1}{6} cdot dfrac{1}{6} cdot = dfrac{5}{6^{3}}$.



However, there other cases where Piper looses, Quincy looses, Riley looses, Piper looses, then Quincy and Riley wins, or where Riley wins before Quincy.



So this can account into what I'm thinking of an infinitely long geometric sequence that later converges to a rational number.



There are many, many more cases. To account for this, I have to keep analyzing all possibilities at each turn, and I believe that eventually I will get some geometric progressions. However, this seems tedious and error prone.



So then I thought that I could just denote the probabilities that I am interested in by letters and write some equations. For instance, if the probability of Piper escaping last is $p$, then after a turn in which nobody escapes the probability of Piper escaping last is still $p$.



This allows me to write the equation: $$p= {5over 6}^3cdot p +text{other cases }.$$



But however, I cannot seem to find that "other cases" thing, and I even further doubted that the $p$ in the equation is stable.



But after some further examination, I find this is not so. I considered first the case with two players: Let $p$ be the probability that the player who starts first escapes first and $q$ the probability that the second player escapes first. I could write the equation $p=1/6+5/6cdot q$ because the probability of the first player escaping is 1/6 plus the probability of him not escaping (5/6) times the probability of him winning as second player, because now the other player rolls the dice first.



Another equation I could write is $p+q=1$ because one of them will escape eventually (with probability 1). Solving this I get $p=1/6+5/6(1-p)$ etc. which leads to $p=6/11$. This is incorrect.



And, after a long time of thoughts, I finally figured the way to write the infinite sum, $p=1/6 + (5/6)^2cdot 1/6+(5/6)^4cdot 1/6+dots$, because the probability of the first player escaping first is 1/6 (if he rolls a double) + (5/6)^2 (=probability of both not rolling a double) times 1/6 (rolling a double at the second turn) and so on...



The sum of that infinite progression is $$p=1/6cdot {1over 1-(5/6)^2}$$ which still gives $6/11$, and is wrong again.



I cannot think of a way to continue. Help please?







probability






share|cite|improve this question













share|cite|improve this question











share|cite|improve this question




share|cite|improve this question










asked 1 hour ago









Max0815Max0815

68918




68918








  • 1




    $begingroup$
    Why do you think $frac6{11}$ is an incorrect answer to the two-player question?
    $endgroup$
    – David K
    1 hour ago










  • $begingroup$
    @DavidK because its not the right answer in relation to the answer key.
    $endgroup$
    – Max0815
    58 mins ago










  • $begingroup$
    You started out working on a problem with three players. If there is an answer key, I would expect it to answer that question. It seems you came up with the two-player problem on your own; how could the answer key anticipate that and give the answer to a question that isn't in the original materials?
    $endgroup$
    – David K
    56 mins ago










  • $begingroup$
    @DavidK Wait I misread your question. There is an answer to the three player one, and I thought you meant that. I was experimenting with the two player one and one of aops' answerers said that it was not right.
    $endgroup$
    – Max0815
    53 mins ago












  • $begingroup$
    You were determining the probability that Piper gets out first, not last. The probability that she gets out last in the two-player game (if she goes first) is $frac{5}{11}$.
    $endgroup$
    – Robert Shore
    50 mins ago
















  • 1




    $begingroup$
    Why do you think $frac6{11}$ is an incorrect answer to the two-player question?
    $endgroup$
    – David K
    1 hour ago










  • $begingroup$
    @DavidK because its not the right answer in relation to the answer key.
    $endgroup$
    – Max0815
    58 mins ago










  • $begingroup$
    You started out working on a problem with three players. If there is an answer key, I would expect it to answer that question. It seems you came up with the two-player problem on your own; how could the answer key anticipate that and give the answer to a question that isn't in the original materials?
    $endgroup$
    – David K
    56 mins ago










  • $begingroup$
    @DavidK Wait I misread your question. There is an answer to the three player one, and I thought you meant that. I was experimenting with the two player one and one of aops' answerers said that it was not right.
    $endgroup$
    – Max0815
    53 mins ago












  • $begingroup$
    You were determining the probability that Piper gets out first, not last. The probability that she gets out last in the two-player game (if she goes first) is $frac{5}{11}$.
    $endgroup$
    – Robert Shore
    50 mins ago










1




1




$begingroup$
Why do you think $frac6{11}$ is an incorrect answer to the two-player question?
$endgroup$
– David K
1 hour ago




$begingroup$
Why do you think $frac6{11}$ is an incorrect answer to the two-player question?
$endgroup$
– David K
1 hour ago












$begingroup$
@DavidK because its not the right answer in relation to the answer key.
$endgroup$
– Max0815
58 mins ago




$begingroup$
@DavidK because its not the right answer in relation to the answer key.
$endgroup$
– Max0815
58 mins ago












$begingroup$
You started out working on a problem with three players. If there is an answer key, I would expect it to answer that question. It seems you came up with the two-player problem on your own; how could the answer key anticipate that and give the answer to a question that isn't in the original materials?
$endgroup$
– David K
56 mins ago




$begingroup$
You started out working on a problem with three players. If there is an answer key, I would expect it to answer that question. It seems you came up with the two-player problem on your own; how could the answer key anticipate that and give the answer to a question that isn't in the original materials?
$endgroup$
– David K
56 mins ago












$begingroup$
@DavidK Wait I misread your question. There is an answer to the three player one, and I thought you meant that. I was experimenting with the two player one and one of aops' answerers said that it was not right.
$endgroup$
– Max0815
53 mins ago






$begingroup$
@DavidK Wait I misread your question. There is an answer to the three player one, and I thought you meant that. I was experimenting with the two player one and one of aops' answerers said that it was not right.
$endgroup$
– Max0815
53 mins ago














$begingroup$
You were determining the probability that Piper gets out first, not last. The probability that she gets out last in the two-player game (if she goes first) is $frac{5}{11}$.
$endgroup$
– Robert Shore
50 mins ago






$begingroup$
You were determining the probability that Piper gets out first, not last. The probability that she gets out last in the two-player game (if she goes first) is $frac{5}{11}$.
$endgroup$
– Robert Shore
50 mins ago












3 Answers
3






active

oldest

votes


















4












$begingroup$

Let $p$ be the probability that Piper escapes first. Her probability of escaping on her first roll by rolling doubles is $frac{1}{6}$.



Let $q$ be the probability that Quincy escapes first. Then before Piper's first roll there is a probability of $frac {1}{6}$ that Quincy has no chance to escape first, and a probability of $frac {5}{6}$ that Quincy's chance of escaping first is $p$ (because if Piper misses then Quincy is now in the same position Piper was in). Thus, $q=frac{5p}{6}$.



Finally, let $r$ be the probability that Riley escapes first. Then before Piper's first roll there is a probability of $frac{11}{36}$ that Riley has no chance to escape first (because either Piper or Quincy or both roll doubles) and a probability of $frac{25}{36}$ that Riley's chance of escaping first is $p$ (because Riley is now in the same position Piper was in). Thus, $r=frac{25p}{36}$.



We also know $p+q+r=1$. Thus,



$$p+frac{5p}{6}+frac{25p}{36}=frac{91p}{36}=1 Rightarrow p=frac{36}{91}, q=frac{30}{91}, r=frac{25}{91}.$$



Edited to add: This doesn't completely answer the question because you asked for the probability that Piper is last to leave, not first to leave. But if Quincy leaves first (which will happen with probability $frac{30}{91}$), you can use the same mode of analysis to determine the probability that Riley beats Piper out of the box ($frac{6}{11}$), and if Riley leaves first (which will happen with probability $frac{25}{91}$), you can use the same mode of analysis to determine the probability that Quincy beats Piper out of the box ($frac{5}{11}$). The answer should turn out to be:



$$frac{30}{91}cdotfrac{6}{11}+ frac{25}{91}cdotfrac{5}{11}=frac{180}{1001}+frac{125}{1001}=frac{305}{1001}.$$






share|cite|improve this answer











$endgroup$









  • 1




    $begingroup$
    Can you explain how you got the 180/1001 and 125/1001 in the last line? Then after I understand it I'll accept! Thanks!
    $endgroup$
    – Max0815
    57 mins ago






  • 1




    $begingroup$
    If Quincy gets out first (which will happen with probability $frac{30}{91}$), then Riley will beat Piper out $frac{6}{11}$ of the time (because Riley goes first in the two-player game that remains). If Riley gets out first (which will happen with probability $frac{25}{91}$), then Quincy will beat Riley out $frac{5}{11}$ of the time (because Piper goes first in the two-player game that remains).
    $endgroup$
    – Robert Shore
    53 mins ago












  • $begingroup$
    +1 thank you very much. Comments will not last, but answers will, even when deleted. Can you please edit that into your answer? Thanks!
    $endgroup$
    – Max0815
    48 mins ago





















1












$begingroup$

At the end of Riley's $n$th turn (that is, after each player has had exactly $n$ turns), each player has a $left(frac56right)^n$ probability to still be in the box.



If Piper is the last to get out, and this happens on her $n+1$st turn, then:




  • at the end of Riley's $n$th turn, Piper was still in the box,

  • at the end of Riley's $n$th turn, Quincy was not still in the box,

  • at the end of Riley's $n$th turn, Riley was not still in the box, and

  • on her $n+1$st turn, Piper rolled the same number on both dice.


You can work out the probability that all four of those events occurred.



If Piper was the last to get out, then it happened on her second turn ($n=1$), or her third turn ($n=2$), or her fourth ($n=3$), ... a list of possibilities for $n = 1$ to infinity, and all are mutually exclusive events so their probabilities can simply be added.



You do not get a geometric series out of this, but with a little manipulation you can get three geometric series, evaluate each one and add them together.






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$endgroup$





















    0












    $begingroup$

    Given that the outcomes of a pair of dice are
    1,1
    2,2
    3,3
    4,4
    5,5
    6,6





    1,2
    1,3
    1,4
    1,5
    1,6
    2,3
    2,4
    2,5
    2,6
    3,4
    3,5
    3,6
    4,5
    4,6
    5,6



    The probability is 6/21 to throw a double pair.



    There exists the probablity of each player throwing a double and therefore getting out of the penalty area in one round of dice throwing so getting back to Piper that is merely 4 throws of the dice if She is the last to get out so



    ( 6 / 21 ) X ( 6 / 21 ) X ( 6 / 21 ) X ( 6 / 21 ) =
    0.00666389004581424406497292794669



    or approx 0.0067% chance. ( WINDOWS CALCULATOR was used here. )



    Regards,



    John O.






    share|cite|improve this answer











    $endgroup$













    • $begingroup$
      There are 36 outcomes when rolling two standard six-sided dice. Any probability with a denominator of 21 is incorrect.
      $endgroup$
      – Nij
      2 mins ago










    • $begingroup$
      @Nij. Rolling a 1 then a 2 is the same outcome as rolling a 2 then a 1 so in fact there are 21 not 36 variations. Write them all down as I have and then count them.
      $endgroup$
      – John Anthony Oliver
      25 secs ago













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    3 Answers
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    3 Answers
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    4












    $begingroup$

    Let $p$ be the probability that Piper escapes first. Her probability of escaping on her first roll by rolling doubles is $frac{1}{6}$.



    Let $q$ be the probability that Quincy escapes first. Then before Piper's first roll there is a probability of $frac {1}{6}$ that Quincy has no chance to escape first, and a probability of $frac {5}{6}$ that Quincy's chance of escaping first is $p$ (because if Piper misses then Quincy is now in the same position Piper was in). Thus, $q=frac{5p}{6}$.



    Finally, let $r$ be the probability that Riley escapes first. Then before Piper's first roll there is a probability of $frac{11}{36}$ that Riley has no chance to escape first (because either Piper or Quincy or both roll doubles) and a probability of $frac{25}{36}$ that Riley's chance of escaping first is $p$ (because Riley is now in the same position Piper was in). Thus, $r=frac{25p}{36}$.



    We also know $p+q+r=1$. Thus,



    $$p+frac{5p}{6}+frac{25p}{36}=frac{91p}{36}=1 Rightarrow p=frac{36}{91}, q=frac{30}{91}, r=frac{25}{91}.$$



    Edited to add: This doesn't completely answer the question because you asked for the probability that Piper is last to leave, not first to leave. But if Quincy leaves first (which will happen with probability $frac{30}{91}$), you can use the same mode of analysis to determine the probability that Riley beats Piper out of the box ($frac{6}{11}$), and if Riley leaves first (which will happen with probability $frac{25}{91}$), you can use the same mode of analysis to determine the probability that Quincy beats Piper out of the box ($frac{5}{11}$). The answer should turn out to be:



    $$frac{30}{91}cdotfrac{6}{11}+ frac{25}{91}cdotfrac{5}{11}=frac{180}{1001}+frac{125}{1001}=frac{305}{1001}.$$






    share|cite|improve this answer











    $endgroup$









    • 1




      $begingroup$
      Can you explain how you got the 180/1001 and 125/1001 in the last line? Then after I understand it I'll accept! Thanks!
      $endgroup$
      – Max0815
      57 mins ago






    • 1




      $begingroup$
      If Quincy gets out first (which will happen with probability $frac{30}{91}$), then Riley will beat Piper out $frac{6}{11}$ of the time (because Riley goes first in the two-player game that remains). If Riley gets out first (which will happen with probability $frac{25}{91}$), then Quincy will beat Riley out $frac{5}{11}$ of the time (because Piper goes first in the two-player game that remains).
      $endgroup$
      – Robert Shore
      53 mins ago












    • $begingroup$
      +1 thank you very much. Comments will not last, but answers will, even when deleted. Can you please edit that into your answer? Thanks!
      $endgroup$
      – Max0815
      48 mins ago


















    4












    $begingroup$

    Let $p$ be the probability that Piper escapes first. Her probability of escaping on her first roll by rolling doubles is $frac{1}{6}$.



    Let $q$ be the probability that Quincy escapes first. Then before Piper's first roll there is a probability of $frac {1}{6}$ that Quincy has no chance to escape first, and a probability of $frac {5}{6}$ that Quincy's chance of escaping first is $p$ (because if Piper misses then Quincy is now in the same position Piper was in). Thus, $q=frac{5p}{6}$.



    Finally, let $r$ be the probability that Riley escapes first. Then before Piper's first roll there is a probability of $frac{11}{36}$ that Riley has no chance to escape first (because either Piper or Quincy or both roll doubles) and a probability of $frac{25}{36}$ that Riley's chance of escaping first is $p$ (because Riley is now in the same position Piper was in). Thus, $r=frac{25p}{36}$.



    We also know $p+q+r=1$. Thus,



    $$p+frac{5p}{6}+frac{25p}{36}=frac{91p}{36}=1 Rightarrow p=frac{36}{91}, q=frac{30}{91}, r=frac{25}{91}.$$



    Edited to add: This doesn't completely answer the question because you asked for the probability that Piper is last to leave, not first to leave. But if Quincy leaves first (which will happen with probability $frac{30}{91}$), you can use the same mode of analysis to determine the probability that Riley beats Piper out of the box ($frac{6}{11}$), and if Riley leaves first (which will happen with probability $frac{25}{91}$), you can use the same mode of analysis to determine the probability that Quincy beats Piper out of the box ($frac{5}{11}$). The answer should turn out to be:



    $$frac{30}{91}cdotfrac{6}{11}+ frac{25}{91}cdotfrac{5}{11}=frac{180}{1001}+frac{125}{1001}=frac{305}{1001}.$$






    share|cite|improve this answer











    $endgroup$









    • 1




      $begingroup$
      Can you explain how you got the 180/1001 and 125/1001 in the last line? Then after I understand it I'll accept! Thanks!
      $endgroup$
      – Max0815
      57 mins ago






    • 1




      $begingroup$
      If Quincy gets out first (which will happen with probability $frac{30}{91}$), then Riley will beat Piper out $frac{6}{11}$ of the time (because Riley goes first in the two-player game that remains). If Riley gets out first (which will happen with probability $frac{25}{91}$), then Quincy will beat Riley out $frac{5}{11}$ of the time (because Piper goes first in the two-player game that remains).
      $endgroup$
      – Robert Shore
      53 mins ago












    • $begingroup$
      +1 thank you very much. Comments will not last, but answers will, even when deleted. Can you please edit that into your answer? Thanks!
      $endgroup$
      – Max0815
      48 mins ago
















    4












    4








    4





    $begingroup$

    Let $p$ be the probability that Piper escapes first. Her probability of escaping on her first roll by rolling doubles is $frac{1}{6}$.



    Let $q$ be the probability that Quincy escapes first. Then before Piper's first roll there is a probability of $frac {1}{6}$ that Quincy has no chance to escape first, and a probability of $frac {5}{6}$ that Quincy's chance of escaping first is $p$ (because if Piper misses then Quincy is now in the same position Piper was in). Thus, $q=frac{5p}{6}$.



    Finally, let $r$ be the probability that Riley escapes first. Then before Piper's first roll there is a probability of $frac{11}{36}$ that Riley has no chance to escape first (because either Piper or Quincy or both roll doubles) and a probability of $frac{25}{36}$ that Riley's chance of escaping first is $p$ (because Riley is now in the same position Piper was in). Thus, $r=frac{25p}{36}$.



    We also know $p+q+r=1$. Thus,



    $$p+frac{5p}{6}+frac{25p}{36}=frac{91p}{36}=1 Rightarrow p=frac{36}{91}, q=frac{30}{91}, r=frac{25}{91}.$$



    Edited to add: This doesn't completely answer the question because you asked for the probability that Piper is last to leave, not first to leave. But if Quincy leaves first (which will happen with probability $frac{30}{91}$), you can use the same mode of analysis to determine the probability that Riley beats Piper out of the box ($frac{6}{11}$), and if Riley leaves first (which will happen with probability $frac{25}{91}$), you can use the same mode of analysis to determine the probability that Quincy beats Piper out of the box ($frac{5}{11}$). The answer should turn out to be:



    $$frac{30}{91}cdotfrac{6}{11}+ frac{25}{91}cdotfrac{5}{11}=frac{180}{1001}+frac{125}{1001}=frac{305}{1001}.$$






    share|cite|improve this answer











    $endgroup$



    Let $p$ be the probability that Piper escapes first. Her probability of escaping on her first roll by rolling doubles is $frac{1}{6}$.



    Let $q$ be the probability that Quincy escapes first. Then before Piper's first roll there is a probability of $frac {1}{6}$ that Quincy has no chance to escape first, and a probability of $frac {5}{6}$ that Quincy's chance of escaping first is $p$ (because if Piper misses then Quincy is now in the same position Piper was in). Thus, $q=frac{5p}{6}$.



    Finally, let $r$ be the probability that Riley escapes first. Then before Piper's first roll there is a probability of $frac{11}{36}$ that Riley has no chance to escape first (because either Piper or Quincy or both roll doubles) and a probability of $frac{25}{36}$ that Riley's chance of escaping first is $p$ (because Riley is now in the same position Piper was in). Thus, $r=frac{25p}{36}$.



    We also know $p+q+r=1$. Thus,



    $$p+frac{5p}{6}+frac{25p}{36}=frac{91p}{36}=1 Rightarrow p=frac{36}{91}, q=frac{30}{91}, r=frac{25}{91}.$$



    Edited to add: This doesn't completely answer the question because you asked for the probability that Piper is last to leave, not first to leave. But if Quincy leaves first (which will happen with probability $frac{30}{91}$), you can use the same mode of analysis to determine the probability that Riley beats Piper out of the box ($frac{6}{11}$), and if Riley leaves first (which will happen with probability $frac{25}{91}$), you can use the same mode of analysis to determine the probability that Quincy beats Piper out of the box ($frac{5}{11}$). The answer should turn out to be:



    $$frac{30}{91}cdotfrac{6}{11}+ frac{25}{91}cdotfrac{5}{11}=frac{180}{1001}+frac{125}{1001}=frac{305}{1001}.$$







    share|cite|improve this answer














    share|cite|improve this answer



    share|cite|improve this answer








    edited 36 mins ago

























    answered 1 hour ago









    Robert ShoreRobert Shore

    2,960218




    2,960218








    • 1




      $begingroup$
      Can you explain how you got the 180/1001 and 125/1001 in the last line? Then after I understand it I'll accept! Thanks!
      $endgroup$
      – Max0815
      57 mins ago






    • 1




      $begingroup$
      If Quincy gets out first (which will happen with probability $frac{30}{91}$), then Riley will beat Piper out $frac{6}{11}$ of the time (because Riley goes first in the two-player game that remains). If Riley gets out first (which will happen with probability $frac{25}{91}$), then Quincy will beat Riley out $frac{5}{11}$ of the time (because Piper goes first in the two-player game that remains).
      $endgroup$
      – Robert Shore
      53 mins ago












    • $begingroup$
      +1 thank you very much. Comments will not last, but answers will, even when deleted. Can you please edit that into your answer? Thanks!
      $endgroup$
      – Max0815
      48 mins ago
















    • 1




      $begingroup$
      Can you explain how you got the 180/1001 and 125/1001 in the last line? Then after I understand it I'll accept! Thanks!
      $endgroup$
      – Max0815
      57 mins ago






    • 1




      $begingroup$
      If Quincy gets out first (which will happen with probability $frac{30}{91}$), then Riley will beat Piper out $frac{6}{11}$ of the time (because Riley goes first in the two-player game that remains). If Riley gets out first (which will happen with probability $frac{25}{91}$), then Quincy will beat Riley out $frac{5}{11}$ of the time (because Piper goes first in the two-player game that remains).
      $endgroup$
      – Robert Shore
      53 mins ago












    • $begingroup$
      +1 thank you very much. Comments will not last, but answers will, even when deleted. Can you please edit that into your answer? Thanks!
      $endgroup$
      – Max0815
      48 mins ago










    1




    1




    $begingroup$
    Can you explain how you got the 180/1001 and 125/1001 in the last line? Then after I understand it I'll accept! Thanks!
    $endgroup$
    – Max0815
    57 mins ago




    $begingroup$
    Can you explain how you got the 180/1001 and 125/1001 in the last line? Then after I understand it I'll accept! Thanks!
    $endgroup$
    – Max0815
    57 mins ago




    1




    1




    $begingroup$
    If Quincy gets out first (which will happen with probability $frac{30}{91}$), then Riley will beat Piper out $frac{6}{11}$ of the time (because Riley goes first in the two-player game that remains). If Riley gets out first (which will happen with probability $frac{25}{91}$), then Quincy will beat Riley out $frac{5}{11}$ of the time (because Piper goes first in the two-player game that remains).
    $endgroup$
    – Robert Shore
    53 mins ago






    $begingroup$
    If Quincy gets out first (which will happen with probability $frac{30}{91}$), then Riley will beat Piper out $frac{6}{11}$ of the time (because Riley goes first in the two-player game that remains). If Riley gets out first (which will happen with probability $frac{25}{91}$), then Quincy will beat Riley out $frac{5}{11}$ of the time (because Piper goes first in the two-player game that remains).
    $endgroup$
    – Robert Shore
    53 mins ago














    $begingroup$
    +1 thank you very much. Comments will not last, but answers will, even when deleted. Can you please edit that into your answer? Thanks!
    $endgroup$
    – Max0815
    48 mins ago






    $begingroup$
    +1 thank you very much. Comments will not last, but answers will, even when deleted. Can you please edit that into your answer? Thanks!
    $endgroup$
    – Max0815
    48 mins ago













    1












    $begingroup$

    At the end of Riley's $n$th turn (that is, after each player has had exactly $n$ turns), each player has a $left(frac56right)^n$ probability to still be in the box.



    If Piper is the last to get out, and this happens on her $n+1$st turn, then:




    • at the end of Riley's $n$th turn, Piper was still in the box,

    • at the end of Riley's $n$th turn, Quincy was not still in the box,

    • at the end of Riley's $n$th turn, Riley was not still in the box, and

    • on her $n+1$st turn, Piper rolled the same number on both dice.


    You can work out the probability that all four of those events occurred.



    If Piper was the last to get out, then it happened on her second turn ($n=1$), or her third turn ($n=2$), or her fourth ($n=3$), ... a list of possibilities for $n = 1$ to infinity, and all are mutually exclusive events so their probabilities can simply be added.



    You do not get a geometric series out of this, but with a little manipulation you can get three geometric series, evaluate each one and add them together.






    share|cite|improve this answer









    $endgroup$


















      1












      $begingroup$

      At the end of Riley's $n$th turn (that is, after each player has had exactly $n$ turns), each player has a $left(frac56right)^n$ probability to still be in the box.



      If Piper is the last to get out, and this happens on her $n+1$st turn, then:




      • at the end of Riley's $n$th turn, Piper was still in the box,

      • at the end of Riley's $n$th turn, Quincy was not still in the box,

      • at the end of Riley's $n$th turn, Riley was not still in the box, and

      • on her $n+1$st turn, Piper rolled the same number on both dice.


      You can work out the probability that all four of those events occurred.



      If Piper was the last to get out, then it happened on her second turn ($n=1$), or her third turn ($n=2$), or her fourth ($n=3$), ... a list of possibilities for $n = 1$ to infinity, and all are mutually exclusive events so their probabilities can simply be added.



      You do not get a geometric series out of this, but with a little manipulation you can get three geometric series, evaluate each one and add them together.






      share|cite|improve this answer









      $endgroup$
















        1












        1








        1





        $begingroup$

        At the end of Riley's $n$th turn (that is, after each player has had exactly $n$ turns), each player has a $left(frac56right)^n$ probability to still be in the box.



        If Piper is the last to get out, and this happens on her $n+1$st turn, then:




        • at the end of Riley's $n$th turn, Piper was still in the box,

        • at the end of Riley's $n$th turn, Quincy was not still in the box,

        • at the end of Riley's $n$th turn, Riley was not still in the box, and

        • on her $n+1$st turn, Piper rolled the same number on both dice.


        You can work out the probability that all four of those events occurred.



        If Piper was the last to get out, then it happened on her second turn ($n=1$), or her third turn ($n=2$), or her fourth ($n=3$), ... a list of possibilities for $n = 1$ to infinity, and all are mutually exclusive events so their probabilities can simply be added.



        You do not get a geometric series out of this, but with a little manipulation you can get three geometric series, evaluate each one and add them together.






        share|cite|improve this answer









        $endgroup$



        At the end of Riley's $n$th turn (that is, after each player has had exactly $n$ turns), each player has a $left(frac56right)^n$ probability to still be in the box.



        If Piper is the last to get out, and this happens on her $n+1$st turn, then:




        • at the end of Riley's $n$th turn, Piper was still in the box,

        • at the end of Riley's $n$th turn, Quincy was not still in the box,

        • at the end of Riley's $n$th turn, Riley was not still in the box, and

        • on her $n+1$st turn, Piper rolled the same number on both dice.


        You can work out the probability that all four of those events occurred.



        If Piper was the last to get out, then it happened on her second turn ($n=1$), or her third turn ($n=2$), or her fourth ($n=3$), ... a list of possibilities for $n = 1$ to infinity, and all are mutually exclusive events so their probabilities can simply be added.



        You do not get a geometric series out of this, but with a little manipulation you can get three geometric series, evaluate each one and add them together.







        share|cite|improve this answer












        share|cite|improve this answer



        share|cite|improve this answer










        answered 47 mins ago









        David KDavid K

        55.1k344120




        55.1k344120























            0












            $begingroup$

            Given that the outcomes of a pair of dice are
            1,1
            2,2
            3,3
            4,4
            5,5
            6,6





            1,2
            1,3
            1,4
            1,5
            1,6
            2,3
            2,4
            2,5
            2,6
            3,4
            3,5
            3,6
            4,5
            4,6
            5,6



            The probability is 6/21 to throw a double pair.



            There exists the probablity of each player throwing a double and therefore getting out of the penalty area in one round of dice throwing so getting back to Piper that is merely 4 throws of the dice if She is the last to get out so



            ( 6 / 21 ) X ( 6 / 21 ) X ( 6 / 21 ) X ( 6 / 21 ) =
            0.00666389004581424406497292794669



            or approx 0.0067% chance. ( WINDOWS CALCULATOR was used here. )



            Regards,



            John O.






            share|cite|improve this answer











            $endgroup$













            • $begingroup$
              There are 36 outcomes when rolling two standard six-sided dice. Any probability with a denominator of 21 is incorrect.
              $endgroup$
              – Nij
              2 mins ago










            • $begingroup$
              @Nij. Rolling a 1 then a 2 is the same outcome as rolling a 2 then a 1 so in fact there are 21 not 36 variations. Write them all down as I have and then count them.
              $endgroup$
              – John Anthony Oliver
              25 secs ago


















            0












            $begingroup$

            Given that the outcomes of a pair of dice are
            1,1
            2,2
            3,3
            4,4
            5,5
            6,6





            1,2
            1,3
            1,4
            1,5
            1,6
            2,3
            2,4
            2,5
            2,6
            3,4
            3,5
            3,6
            4,5
            4,6
            5,6



            The probability is 6/21 to throw a double pair.



            There exists the probablity of each player throwing a double and therefore getting out of the penalty area in one round of dice throwing so getting back to Piper that is merely 4 throws of the dice if She is the last to get out so



            ( 6 / 21 ) X ( 6 / 21 ) X ( 6 / 21 ) X ( 6 / 21 ) =
            0.00666389004581424406497292794669



            or approx 0.0067% chance. ( WINDOWS CALCULATOR was used here. )



            Regards,



            John O.






            share|cite|improve this answer











            $endgroup$













            • $begingroup$
              There are 36 outcomes when rolling two standard six-sided dice. Any probability with a denominator of 21 is incorrect.
              $endgroup$
              – Nij
              2 mins ago










            • $begingroup$
              @Nij. Rolling a 1 then a 2 is the same outcome as rolling a 2 then a 1 so in fact there are 21 not 36 variations. Write them all down as I have and then count them.
              $endgroup$
              – John Anthony Oliver
              25 secs ago
















            0












            0








            0





            $begingroup$

            Given that the outcomes of a pair of dice are
            1,1
            2,2
            3,3
            4,4
            5,5
            6,6





            1,2
            1,3
            1,4
            1,5
            1,6
            2,3
            2,4
            2,5
            2,6
            3,4
            3,5
            3,6
            4,5
            4,6
            5,6



            The probability is 6/21 to throw a double pair.



            There exists the probablity of each player throwing a double and therefore getting out of the penalty area in one round of dice throwing so getting back to Piper that is merely 4 throws of the dice if She is the last to get out so



            ( 6 / 21 ) X ( 6 / 21 ) X ( 6 / 21 ) X ( 6 / 21 ) =
            0.00666389004581424406497292794669



            or approx 0.0067% chance. ( WINDOWS CALCULATOR was used here. )



            Regards,



            John O.






            share|cite|improve this answer











            $endgroup$



            Given that the outcomes of a pair of dice are
            1,1
            2,2
            3,3
            4,4
            5,5
            6,6





            1,2
            1,3
            1,4
            1,5
            1,6
            2,3
            2,4
            2,5
            2,6
            3,4
            3,5
            3,6
            4,5
            4,6
            5,6



            The probability is 6/21 to throw a double pair.



            There exists the probablity of each player throwing a double and therefore getting out of the penalty area in one round of dice throwing so getting back to Piper that is merely 4 throws of the dice if She is the last to get out so



            ( 6 / 21 ) X ( 6 / 21 ) X ( 6 / 21 ) X ( 6 / 21 ) =
            0.00666389004581424406497292794669



            or approx 0.0067% chance. ( WINDOWS CALCULATOR was used here. )



            Regards,



            John O.







            share|cite|improve this answer














            share|cite|improve this answer



            share|cite|improve this answer








            edited 10 mins ago

























            answered 24 mins ago









            John Anthony OliverJohn Anthony Oliver

            525




            525












            • $begingroup$
              There are 36 outcomes when rolling two standard six-sided dice. Any probability with a denominator of 21 is incorrect.
              $endgroup$
              – Nij
              2 mins ago










            • $begingroup$
              @Nij. Rolling a 1 then a 2 is the same outcome as rolling a 2 then a 1 so in fact there are 21 not 36 variations. Write them all down as I have and then count them.
              $endgroup$
              – John Anthony Oliver
              25 secs ago




















            • $begingroup$
              There are 36 outcomes when rolling two standard six-sided dice. Any probability with a denominator of 21 is incorrect.
              $endgroup$
              – Nij
              2 mins ago










            • $begingroup$
              @Nij. Rolling a 1 then a 2 is the same outcome as rolling a 2 then a 1 so in fact there are 21 not 36 variations. Write them all down as I have and then count them.
              $endgroup$
              – John Anthony Oliver
              25 secs ago


















            $begingroup$
            There are 36 outcomes when rolling two standard six-sided dice. Any probability with a denominator of 21 is incorrect.
            $endgroup$
            – Nij
            2 mins ago




            $begingroup$
            There are 36 outcomes when rolling two standard six-sided dice. Any probability with a denominator of 21 is incorrect.
            $endgroup$
            – Nij
            2 mins ago












            $begingroup$
            @Nij. Rolling a 1 then a 2 is the same outcome as rolling a 2 then a 1 so in fact there are 21 not 36 variations. Write them all down as I have and then count them.
            $endgroup$
            – John Anthony Oliver
            25 secs ago






            $begingroup$
            @Nij. Rolling a 1 then a 2 is the same outcome as rolling a 2 then a 1 so in fact there are 21 not 36 variations. Write them all down as I have and then count them.
            $endgroup$
            – John Anthony Oliver
            25 secs ago




















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