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Puzzle of the Day

These puzzles are also printed in Eight days a week, a booklet published by the Association of Teachers of Mathematics.

This is a game for two. Start by writing zero. The first player adds 1, 2, or 10 and writes the answer. The second player adds 1, 2, or 10 to this answer and writes the new number, and so on. The winner is the first to reach 20.

Answer: best strategy is to aim to get to 2, 5, 8, 11, 14, 17