Let S be a set of 5 elements and P(S) denote the power set of S. Let E be an event of choosing an ordered pair (A, B) from the set P(S) P(S) such that A B = . If the probability of the event E is 3p2q, where p, q N, then p + q is equal to .
Answer
15
Solution
Total ordered pairs (A, B): n(P(S))2 = (25)2 = 210
For A B = , each element of S has 3 choices:
in A only, in B only, or in neither.
favourable pairs = 35
P(E) = 35210
p = 5, q = 10
p + q = 15
Answer: 15