Alex flips a fair coin 20 times. Bert spins a fair coin 21
times. Bert wins if he gets more heads than Alex, else Alex wins.
Note that Alex wins if there is a tie. What is the probability that
Bert wins?
B flips his 21 coins and he gets H heads and T tails.
A flips his 20 coins and gets H' heads and T' tails.
Either H>H' (and then T<=T') or T>T' (and then H<=H'), so
by symmetry B will either have more heads or more tails than B, but not
both.
His chances are 50%-50% of winning.
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Posted by Oskar
on 2004-05-20 14:17:57 |
Answer
