Let A and B be two disjoint events such that PA 14 and PB

Let A and B be two disjoint events such that P(A) = 1/4 and P(B) = 2/3, then P(A B) is

equal to:

(a) 0

(b) 1/6

(c) 5/6

(d) 11/12

(e) None of the above

Solution

If they are disjoint, P(A n B) = 0. Thus,

P(A U B) = P(A) + P(B) - P(A n B)

= (1/4) + (2/3) - 0

= 11/12 [ANSWER, D]