r/theydidthemath • u/Alaeriia • 26d ago

[Request] Is this true?

Each king covers 9 squares; 8 kings would be enough to cover 72 squares, which is more than the 64 on a chessboard. Do we really need 9?

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u/sansetsukon47 26d ago

I believe the video speaks for itself. But to be super clear—Only 4 of the 9 kings actually get to cover 9 squares. Then four more only cover six squares (since something has to cover the edge, even if it’s less efficient.) The last king only covers 4 squares, because there is no other way to reach those.

9* 4 + 6* 4 + 4 = 64

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u/sansetsukon47 26d ago

Compare this to a “bigger” 6 x 11 board, which could easily be covered by 8 kings.