MathDB
License plate

Source:

November 28, 2005
probabilitynumber theoryrelatively prime

Problem Statement

Many states use a sequence of three letters followed by a sequence of three digits as their standard license-plate pattern. Given that each three-letter three-digit arrangement is equally likely, the probability that such a license plate will contain at least one palindrome (a three-letter arrangement or a three-digit arrangement that reads the same left-to-right as it does right-to-left) is m/nm/n, where mm and nn are relatively prime positive integers. Find m+nm+n.