Removing Numbers On A Blackboard
Source: Bundeswettbewerb Mathematik 2017, Round 1 - #1
August 7, 2017
blackboardcombinatoricscombinatorics unsolvednumber theorynumber theory unsolveddivisibleDivisibility
Problem Statement
The numbers are on the blackboard. Amelie and Boris take turns removing one of those until only two numbers remain on the board. Amelie starts. If the sum of the last two numbers is divisible by , then Amelie wins. Else Boris wins. Who can force a victory?