Date: Fri, 22 Nov 1996 17:42:33 -0500

From: Alex Bogomolny

The simplest way is to first compute the probability that 'A' will not be selected. For a single rep display, this probability is (x-1)/x. For two reps display, it's [(x-1)/x]^{2}. For n reps display, it's [(x-1)/x]^{n}. Therefore, the probability that 'A' will show up at least once is 1-[(x-1)/x]^{n}.