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Question
If E and F are events such that P(E) = `1/4`, P(F) = `1/2` and P(E and F) = `1/8`, find
- P(E or F)
- P(not E and not F).
Solution
P(E) = `1/4`, P(F) = `1/2`, P(E and F) = P(E ∩ B) = `1/8`
(i) P (E) or F) = P(E U F) = P(E) + P(F) – P(E ∩ F)
= `1/4 + 1/2 - 1/8`
= `(2 + 4 - 1)/8`
= `5/8`
(ii) P(not E and not F) = P(E ∩ F)
= P[(E ∪ F)'] = 1 – P(E ∪ F)
= `1 - 5/8`
= `3/8`
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