Question

Of the 1,000 students in a local college, 420 own brand X mobile phones and 580 own brand Y mobile phones. Of these students, 80 own both brands of mobile phones. Find the probability that a student chosen at random has a brand X mobile phone given that he has a brand Y mobile phone.
A. 2/14

B. 5/21

C. 3/28

D. 4/29

Answer 1

P(X \ Y) = P(X ∩ Y)/P(Y)
P(X ∩ Y) = 80/1000 = 0.08
P(Y) = 580/1000 = 0.58

P(X \ Y) = 0.08/0.58 = 8/58 = 4/29