Maths Challenge Puzzle

Maths related puzzles can provide a simple and focussed challenge - performing mental arithmetic as quickly as you can without making mistakes can actually be quite good fun!

Here are three maths challenge puzzles for you, an easy, a moderate and a hard puzzle. See if you can do them within a minute. The level of these is very fair with only a gentle increase in difficulty at each stage, so none of the calculations expected are unreasonable such as calculating 37.5% of a number or squaring 34! If you want harder ones, let me know.