On Pages 55/56 of Murderous Maths: Guaranteed to Mash Your Mind

Professor Fiendish sets this diabolical puzzle:

## A chessboard has 8x8 little squares which makes 64 squares altogether.We divide it up into four pieces as shown by the red lines. (You can test this by drawing it on paper and then cutting the four shapes out.) | |

## Now you move the pieces around and make this shape.If you're using a chessboard then you'll find you get two black squares or two white squares together, and some split coloured squares. Just to make it neater we'll reverse the colours of the two pieces on the left hand side... | |

## ...there! That's nice.There's just one little problem. We started with 64 squares. Now we've got 13 squares along the bottom and 5 up the side. The total number of squares is now
## Where did the extra square come from? |

*Give up? Then click on the picture of the Professor to find out!*