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2020 AMC 12B Question 14

AMC12 · 2020 AMC 12B

Question 14

Bela and Jenn play the following game on the closed interval $[0, n]$ of the real number line, where $n$ is a fixed integer greater than $4.$ They take turns playing, with Bela going first. At his first turn, Bela chooses any real number in the interval $[0, n].$ Thereafter, the player whose turn it is chooses a real number that is more than one unit away from all numbers previously chosen by either player. A player unable to choose such a number loses. Using optimal strategy, which player will win the game?
  1. Bela will always win.
  2. Jenn will always win.
  3. Bela will win if and only if $n$ is odd.
  4. Jenn will win if and only if $n$ is odd.
  5. Jenn will win if and only if $n \gt 8.$