Interview Question

Researcher Interview

Two gamblers are playing a coin toss game. Gamer A has

  (n+1) fair coins, B has n fair coins. What is the probability that A will have more than B if both flip all their coins?

Interview Answer

2 Answers



Interview Candidate on Dec 7, 2011

To see the reason, consider 1 coin from A separately. It is either H or T. If it is H, the A wins if he has at least as many heads as B in the rest of the n coins. If it is T, then B wins if he has at least as many H in the rest of n coins. This is symmetrical and therefore the probability of A winining is 0.5.

someone on Dec 21, 2011

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