480.Halving Coins to a Perfect Finish
★★★classical probabilityCh. 2 — Axiomatic and Conditional Probability444+ Problems in Probability
25 fair coins are flipped simultaneously. All coins showing tails are removed, and the survivors are flipped again — repeating until either no coins remain or all remaining coins show heads (with at least one coin present), which counts as a win. What is the probability you win?
Sign in to submit an answer and track it toward your stats.
Sign inHint
Compute the win probability for 1 coin, then 2. A pattern this clean demands induction.
Want timed drills, mental math, and a market-making game too? Try the full practice suite →