 Solution

ID: past-exam-of-the-mathematics-course-of-the-year-1-of-the-natural-sciences-course-of-the-university-of-cambridge/2009/paper-2/17/c/iv/solution

The two-event inclusion-exclusion principle subtracts the overlap counted twice:

P (A) + P (B) - P (A \cap B) = P (A \cup B) .

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