Expected flips after a losing start
You flip a fair coin repeatedly until the first head appears. A friend peeks and tells you the very first flip came up tails. Given that, what is the expected total number of flips (counting the tail you already spent)?
Show hints (2)+
- First find the unconditional expected flips via a self-referential equation.
- After a tail the coin is memoryless - add the flip you spent to a fresh expected wait.
Answer
Reveal answer →Final answer
3
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Asked at: Timed Mental-Math & Sequences, Game-Based Aptitude