# Math

Suppose you decided to keep flipping a coin until it came up tails. Which of these is most likely?

a.flipping the coin 11 times
b.flipping the coin 12 times
c.flipping the coin 14 times
d.flipping the coin 13 times

1. all are equal.
if one the tenth, to flip again, pr(tail)=1/2
if you didn't get it on the tenth, the pr(tail)=1/2 and so on.
no matter how long previous flips have gone, the prob of a tail on one more flip is the same, 1/2.

posted by bobpursley
2. P(n Heads,Tail) = (1/2)n * 1/2 = (1/2)^(n+1)

posted by Steve

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