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2021 AMC 12B Question 22

AMC12 · 2021 AMC 12B

Question 22

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 $4$ and $2$ can be changed into any of the following by one move: $(3,2),$ $\ (2,1,2),$ $\ (4),$ $\ (4,1),$ $\ (2,2),$ or $(1,1,2).$

Question illustration

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?
  1. $(6,1,1)$
  2. $(6,2,1)$
  3. $(6,2,2)$
  4. $(6,3,1)$
  5. $(6,3,2)$