Repeat Square Puzzle

This is a novel puzzle.  You hand over four cut out pieces to a spectator to form into a perfect square. This is relatively easy, and the spectator will form the square with a few attempts. As an after thought, you hand him another piece – a small square.  Now ask him to form a perfect square using all five pieces. This will prove much more difficult, until you demonstrate how easy it is. Made in plastic, with instructions.