At the movies, 60% of the moviegoers bought a soda. 45% of the moviegoers bought popcorn and soda. What is the probability that a person will buy popcorn if they have already decided to buy soda?

Question

answer choices:

3/4

9/20

3/50

27/100

Answer 1

This is a problem using the conditional probability formula:

Pr ( event A occurs given event B occurs ) = Pr ( both event A and B occur ) / Pr ( event B occurs )

Let P be event the moviegoer purchased popcorn and S the event moviegoer purchased soda. Then

Pr ( S ) = .60 Also Pr ( P and S ) = .45 So

Pr ( P given S ) = .45 / .60 = .75