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(At least one head in 3 flips)
Find P(at least one head) when flipping a coin 3 times.
Counting "at least one head" directly requires listing many outcomes. Instead, use the complement: P(at least one head) = 1 - P(no heads).
P(no heads) = P(all tails) = P(TTT) = (1/2)³ = 1/8.
P(at least one head) = 1 - 1/8 = 7/8.
