Three fair coins are tossed. Given that at least one shows heads, what is the probability that exactly two show heads?
Answer and explanation
Correct answer: C.
- Step 1: There are equally likely outcomes, and only has no head, so outcomes satisfy the condition. Step 2. Exactly two heads can occur in ways, so the conditional probability is . **Answer: . Why not the others:** ignores the condition, treats the coins separately, and uses the wrong restricted sample space.
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