Can you use the clues to complete these 4 by 4 Mathematical Sudokus?

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?

Which pairs of cogs let the coloured tooth touch every tooth on the other cog? Which pairs do not let this happen? Why?

Take three consecutive numbers and add them together. What do you notice?

These points all mark the vertices (corners) of ten hidden squares. Can you find the 10 hidden squares?

What can you see? What do you notice? What questions can you ask?