The manager of a Drug Store knows that 50% of the customers entering the store buy prescription drugs, 65% buy over-the-counter drugs, and 18% buy both types of drugs. What is the probability that a randomly selected customer will buy at least one of these two types of drugs?

A).5
B).85
C).97
D)1.0

2 answers

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Prob(A OR B) = Prob(A) + Prob(B) - Prob(A AND B)
= .5 + .65 - .18
= .97

looks like C)