Brain Teasers & Mental Math
Two players alternately flip a fair coin; the first to flip heads wins. What is the probability the player who goes first wins?
Model answer
The first player wins on flip 1 (prob 1/2), or both miss their first flip and we're back to the start with the roles reset. So P = 1/2 + (1/2)²·P, giving P(1 − 1/4) = 1/2 → P = (1/2)/(3/4) =…
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