This conundrum has been puzzling people for over a century. A scientific study found that most university students could not solve the puzzle in 15 minutes, and they needed hints to finish it.
There are a few things that people often get wrong with this puzzle. It is very tempting to fill the gap in the 5-sided piece. The gap is a right angle and each of the other pieces will fit in there. But the gap is a red herring. You have to leave it empty to solve the puzzle.
People also want to put all the pieces running left to right, or up and down. A T shape is made of horizontal and vertical lines, but in order to solve the puzzle the 5-sided piece needs to be on a 45° angle.
The 5-sided shape is the key piece. When a group of students were given this puzzle with the 5-sided shape in the right place they all solved the puzzle in minutes. Without this hint, the puzzle usually takes a lot longer. Famous mathematical journalist Martin Gardner once said, “I know of no polygon-dissection puzzle with as few pieces that is so intractable.”
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