| A normal sized chess-board is made of 64 squares (8 x 8). Since there are only 60 squares in a full set of pentominoes it would not be possible to use them to cover a complete chess-board. However it is possible to cover a chess-board provided a 'hole' of 4 squares (2 x 2) is left in it. One example of that is shown on the right. It always possible to find a solution no matter where the hole is placed on the board. |  |
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| 22. | Find a solution to covering the chess-board when the hole is placed exactly in the middle. | |