Let X be a set containing n elements. If two subsets A and B of X are picked at random, the probability that A and B have the same number of elements is
The Attempt at a Solution
Total number of subsets possible is 2^n. Now the subsets containing 1 element=n. For 2 elements it is n(n-1). Similarly for n elements it is n!. Now A and B can belong to any one of the above.