Fair game - ISL 1986
Source:
August 31, 2010
probabilitycombinatoricsgamegame strategycountingIMO Shortlist
Problem Statement
Three persons , are playing the following game:A -element subset of the set is randomly chosen, with an equal probability of each choice, where is a fixed positive integer less than or equal to . The winner is or , respectively, if the sum of the chosen numbers leaves a remainder of , or when divided by .For what values of is this game a fair one? (A game is fair if the three outcomes are equally probable.)