The reason this puzzle is called a Fibonacci puzzle is because all of the lengths 3, 5, 8, and 13 mentioned above are Fibonacci numbers. In fact, given four consecutive Fibonacci numbers, you can build a puzzle in the same manner as described above. If you start with the Fibonacci numbers 5, 8, 13, and 21, draw the resulting two rectangles; one is a 13 by 13 square and the other is an 8 by 21 rectangle. Divide both into the appropriate four pieces.