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Nabu's Knee-knocker SignSolution


  • A 4 x 4 grid board has 16 squares, so you need to use four T-tetrominoes to cover it. One way to do this is shown here with the four T-tetominoes in different colors.


  • A 5 x 5 grid board has 25 squares. Six T-tetrominoes would cover 24 squares and seven T-tetrominoes would cover 28 squares. We can't cover just 25 squares.

  • View the 6 x 6 grid board colored as a checker board with black and white squares.


    A T-tetromino would cover 1 white and 3 black squares () or would cover 1 black and 3 white squares ().

    Since half the grid squares are black and half are white, a cover would need half the T-tetrominoes covering 1 white and 3 black squares and half covering 1 black and 3 white squares. A 6 x 6 grid contains 36 grid squares and would need 9 T-tetrominoes to cover it (4 x 9 = 36). But 9 is an odd number and can't be divided in half (with whole numbers) so you can't cover a 6 x 6 grid board with T-tetrominoes.


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