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AMC 12 2013b Problem 18

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Barbara and Jenna play the following game, in which they take turns. A number of coins lie on a table. When it is Barbara's turn, she must remove 22 or 44 coins, unless only one coin remains, in which case she loses her turn. When it is Jenna's turn, she must remove 11 or 33 coins. A coin flip determines who goes first. Whoever removes the last coin wins the game. Assume both players use their best strategy. Who will win when the game starts with 20132013 coins and when the game starts with 20142014 coins?

Whoever goes first will win with 20132013 coins, and whoever goes second will win with 20142014 coins.

\textbf{(A)}BarbarawillwinwithBarbara will win with2013coinsandJennawillwinwithcoins and Jenna will win with2014coins.coins.\textbf{(B)}JennawillwinwithJenna will win with2013coins,andwhoevergoesfirstwillwinwithcoins, and whoever goes first will win with2014coins.coins.\textbf{(C)}BarbarawillwinwithBarbara will win with2013coins,andwhoevergoessecondwillwinwithcoins, and whoever goes second will win with2014coins.coins.\textbf{(D)}JennawillwinwithJenna will win with2013coins,andBarbarawillwinwithcoins, and Barbara will win with2014coins.coins.\textbf{(E)}

Dataset text AMC 12 2000 to 2025. Quoted with source.

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