# Work in pairs on the following version of a game called NIM. A calculator is needed for each pair.?

Try Reverse NIM using the digits 3, 5, and 7 and starting with 73 on the display. The first player to display a negative number loses. What is the winning strategy?

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- hayharbrLv 710 years agoBest Answer
You'd lose if it was your turn and the calculator showed 2 or less. In order for your opponent to have made a 2 or less, the display at her turn would have to be 9 or less meaning you'd lose unless you could give her the calculator with 10 on it. And so also you want to give it to her with 20 on it (since whatever she enters next, you can enter something to make it 10) And 30, and 40, and 50, and 60, and 70. So you win by going first and subtracting 3.

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