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If A and B are two events associated with a random experiment such that P (A ∪ B) = 0.8, P (A ∩ B) = 0.3 and P (A′) = 0.5, find P(B). |
Answer» Given: A and B are two events. P (A′) = 0.5, P (A ∩ B) = 0.3 and P (A ∪ B) = 0.8 Since, P (A′) = 1 – P (A) P (A) = 1 – 0.5 = 0.5 Now we need to find P (B). By definition of P (A or B) under axiomatic approach (also called addition theorem) we know that: P (A ∪ B) = P (A) + P (B) – P (A ∩ B) So, P (B) = P (A ∪ B) + P (A ∩ B) – P (A) P (B) = 0.8 + 0.3 – 0.5 = 1.1 – 0.5 = 0.6 ∴ P (B) is 0.6 |
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