Order 21 Perfect Square Dissection

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A Square which can be Dissected into a number of smaller Squares with no two equal is called a Perfect Square Dissection (or a Squared Square).
The order is the number of elements (squares) used in the dissection. Historically, the first perfect dissection was described by Sprague in 1939. Since then, many solutions have been found, with a goal being to find the one with the smallest order. Bouwkamp demonstrated that there is no possible dissection if the order is less than 21.
In 1948, a perfect square of order 24 was found by Willcocks followed in 1964 by Wilson with a perfect square of order 25. In 1967, five perfect squares of order 25 were published by Wilson in his thesis. Finally, Duijvestijn found a solution of order 21 in 1978 with the aid of a DEC-10 computer. This solution is the only one of minimum order 21 (except for symmetries).

This puzzle is the unique simple perfect square of order 21 (the lowest possible order), discovered. Duijvestijn. It is composed of 21 squares with total side length 112 units.
We urge you to explore further this concept in mathematics by doing web searches on "Perfect Square Dissections".
This puzzle comes with 20 squares with the 21st square shown on the frame. The smallest
square is too small to effectively handle so that if you get the 20 pieces in you will have an opening
of that tiny size. It is extremely challenging, particularly if you have not previously seen the solution.

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Видео Order 21 Perfect Square Dissection канала Dave Janelle