438.One Fair Coin Saves Parity
★★★classical probabilityCh. 2 — Axiomatic and Conditional Probability444+ Problems in Probability
coins are laid out in front of you. One is fair; the other each show heads with probability , where . All coins are flipped. Find the probability that an even number of heads appears.
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Condition on the biased coins first. What does the single fair coin do to the parity?
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