CA Foundation P3 · Chapter 15 · Question 3 of 9
If P(A) = 0.5, P(B) = 0.4 and P(A ∩ B) = 0.2, then P(A ∪ B) is:
Test yourself: pick an answer
Reveal answer & explanation
Correct answer: A) 0.7
Explanation
By the addition theorem, P(A ∪ B) = P(A) + P(B) − P(A ∩ B) = 0.5 + 0.4 − 0.2 = 0.7. Simply adding gives 0.9, which double counts the overlap.
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