|The remaining piece [Solution]
There are two ways to solve this puzzle; the hard way or the
easy way. The hard way is to actually solve it and discover
what is the piece; the easy way is counting the white squares
(35) and adding up all the areas of the pieces (38): this way
one would find that the extra piece has an area of 3 squares
and there is only one piece with that area (the rightmost one).