Events A and B are independent with P(A) = 3/10 and P(B) = 1/2. What is the probability that at least one of them occurs?
Answer and explanation
Correct answer: B. 13/20
- Step 1: P(A and B) = 3/10 x 1/2 = 3/20. Step 2. P(A or B) = P(A) + P(B) - P(A and B) = 3/10 + 1/2 - 3/20 = 13/20. Answer: 13/20. Why not the others: 4/5: That adds the probabilities and counts the overlap twice. 3/20: That is the probability that both occur. 7/20: That is the probability that neither occurs.
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