Question

Suppose that of all individuals buying a certain digital camera,60% include an optional memory card in their purchase, 40%include an extra battery, and 30% include both a card and battery.1A randomly selected buyer is known to have purchased anextra battery. Find the probability that an optional card wasalso purchased.2A randomly selected buyer is known to have purchased anoptional card. Find the probability that an extra battery wasalso purchased.

Answer 1

1A) 0.75

2A) 0.5

Explanation:

Let A be an event of include an optional memory card

B be an event of include an extra battery

P(A) = 0.6

P(B) = 0.4

P(A and B) = 0.3

1A) P(A|B) = P(A and B) /P(B) = 0.3 / 0.4 = 0.75

2A) P(B|A) = P(A and B)/P(A) = 0.3/0.6= 0.5