Here's some interesting maths homework that my son got.

Using only four 4s and whichever operators you choose, come up with sums that equal every number from 1 to 20.

For example, 16 is 4 + 4 + 4 + 4. And 2 is (4/4) + (4/4).

5 is (√4 x √4) + 1. And 8 is 4 + 4 + 4 - 4.

We've got answers for most of them, but are struggling with a few. Haven't got his book in front of me now, but I think we don't have an answer for 10, for example.

PS: You must use all 4 fours.

EDIT: 5 is (√4 x √4) + (4/4)