Here is a simple or complex – depending upon your perspective – puzzle. It is complex if you try to enumerate all possibilities. There is a very simple and elegant way though.
As always, if you are reading this on FB, do not post your answer on Comments section. Sent me a message.
Question: In a simple 8 by 8 chessboard, how many rectangles are there?
As you can imagine a rectangle can be one square by one square – and there are 64 of them – (squares are rectangles) or two squares by one square (and there are quite a few of them) or three squares by five squares and such….