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From Amusements in Mathematics by Henry Ernest Dudeney.

The moves are made by exchanges of opposite colours standing on the same line. Thus, G and J may exchange places, or F and A, but you cannot exchange G and C, or F and D, because in one case they are both white and in the other case both black. Can you bring about the required arrangement in seventeen exchanges?

[Illustration]

It cannot be done in fewer moves. The puzzle is really much easier than it looks, if properly attacked.

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A B C D E F G H I J K L: Amusements in Mathematics by Henry Ernest Dudeney | amphi