Question 180108
Suppose that 48% of the women who gave birth at a certain hospital last year were over 30 years old, and that 46% were unmarried. If 65% of the women were over 30 or unmarried (or both), what is the probability that a woman who gave birth at the hospital was both unmarried and over 30 ? 
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Formula: P(A and B) = P(A) + P(B) - P(A or B)
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Your problem:
P(un and >30) = P(un) + P(>30) - P(un or >30)
P(un and >30) = 0.46 + 0.48 - 0.65 = 0.29
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Cheers,
Stan H.