Counting and the reflection principle

Abstract

In her Gazette article on “Roll-a-penny probabilities”, Ann Hirst sets out to find the probability that a player will lose after a certain number of rolls. She considers only the simplest case where the player starts with one penny, and solves the problem by setting up a recurrence relation and using induction. The problem of what happens if the player starts with more than one penny is left for the further consideration of the reader.