Challenge Level

In this 100 square, look at the green square which contains the numbers 2, 3, 12 and 13. What is the sum of the numbers that are diagonally opposite each other? What do you notice?

Challenge Level

Can you find pairs of differently sized windows that cost the same?

Challenge Level

There are lots of different methods to find out what the shapes are worth - how many can you find?

Challenge Level

How many solutions can you find to this sum? Each of the different letters stands for a different number.