I find probability questions interesting, because they often defy intuition. Particularly for me are those that involve waiting times. Other than the basic idea of an event of probability p needing on average 1/p trials to occur. But here's one not that trivial, yet still fairly easy to solve -- with the right approach.

On average, how many times do you need to flip a fair coin before you have seen a (continuous) run of an odd number of heads followed by a tail?

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## bonanova

I find probability questions interesting, because they often defy intuition. Particularly for me are those that involve waiting times. Other than the basic idea of an event of probability p needing on average 1/p trials to occur. But here's one not that trivial, yet still fairly easy to solve -- with the right approach.

On average, how many times do you need to flip a fair coin before you have seen a (continuous) run of an odd number of heads followed by a tail?

For example, T T H H H H T

H H H Ttook 11 flips.Edited by bonanovaclarification

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