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Roll the Die Higher (Posted on 2005-04-07) Difficulty: 3 of 5
Two players alternate throwing a six-sided die. The first player who fails to roll a higher number than the preceding roll loses. What is the probability that the first player wins?

What if the die is n-sided?

See The Solution Submitted by Charlie    
Rating: 3.8571 (7 votes)

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Solution General Result | Comment 7 of 13 |
If you are using an n-sided die, and the last roll was not a losing  roll,  and there are k numbers available that are higher than the last number rolled, then the person who is not about to roll has a probability of winning of p(k) = ((n-1)/n)^k and other person has a probability of winning of 1-((n-1)/n)^k.

In particular, at the start of the game, the second player has probability ((n-1)/n)^n of winning.  This was Fredericko's theory.

I unfortunately was no longer logged in when I tried and failed to post a proof of this, lost the whole thing, and I don't feel like retyping it.  I did a proof by induction on k.



  Posted by Steve Herman on 2005-04-08 15:39:50
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