Wandering Token
Source: 2014 AIME I Problem 11
March 14, 2014
analytic geometryprobabilitysymmetryAMCAIMErotationgeometry
Problem Statement
A token starts at the point of an -coordinate grid and them makes a sequence of six moves. Each move is unit in a direction parallel to one of the coordinate axes. Each move is selected randomly from the four possible directions and independently of the other moves. The probability the token ends at a point on the graph of is , where and are relatively prime positive integers. Find .