MathCastle
Proof Writing & Problem SolvingEasy

Proof Writing & Problem Solving · Easy problem

One cell is removed from a 5×55 \times 5 board, and the remaining 24 cells are to be tiled by 1×21 \times 2 dominoes. Colour the board like a chessboard with dark corners. The colouring argument shows the removed cell must be of one colour. How many cells of the board have that colour?

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