You can move the 4 pieces of this jigsaw around and fit them into the outlines shown below. Try for yourself with this interactivity. One square unit is missing in the lower shape.
If you can see this message Flash may not be working in your browser
Please see http://nrich.maths.org/techhelp/#flash to enable it.
Explain what has happened to the missing area? (Of course muggles magic is not magic at all!)
Puzzles such as these first appeared in Zeitschrift für Mathematik und Physik Leipzig, 1868, vol XIII, page 162, although Martin Gardner states that Sam Lloyd the Elder, (there were two, father and son, who were both great puzzle producers and publishers in England) also talked about them around 1865. This particular one seems to have been invented by Roy Nauw of Kloetinge,
from whom permission is being sought.