AMC 10 Step by Step
2021 AMC 10BProblem 24P21-25~10 minPrint

Arjun and Beth play a game in which they take turns removing one brick or two adjacent bricks from one "wall" among a set of several walls of bricks, with gaps possibly creating new walls. The walls are one brick tall. For example, a set of walls of sizes 44 and 22 can be changed into any of the following by one move: (3,2),(2,1,2),(4),(4,1),(2,2),(3,2),(2,1,2),(4),(4,1),(2,2), or (1,1,2).(1,1,2).

figure

Arjun plays first, and the player who removes the last brick wins. For which starting configuration is there a strategy that guarantees a win for Beth?

Log in to save your progress.

Similar problems

Problem © Mathematical Association of America (MAA), American Mathematics Competitions. Reproduced for non-commercial educational use. Solution and commentary are original to this site.