MathDB
Probability of sets

Source: AIME II 2007 #10

March 29, 2007
AIMEcombinatorics

Problem Statement

Let SS be a set with six elements. Let PP be the set of all subsets of S.S. Subsets AA and BB of SS, not necessarily distinct, are chosen independently and at random from PP. the probability that BB is contained in at least one of AA or SAS-A is mnr,\frac{m}{n^{r}}, where mm, nn, and rr are positive integers, nn is prime, and mm and nn are relatively prime. Find m+n+r.m+n+r. (The set SAS-A is the set of all elements of SS which are not in A.A.)