By Warwick:
Can you solve this puzzle? Use exactly four 4’s to form every integer from 1 to 12, using only the operators +, -, x, / and square root.

For example, 4/4 – 4/4 = 0

– You cannot string 4’s together to make 44
– You cannot use just three four’s or five – it must be exactly four of them
– Try to do it without Googling – with a bit of thought it’s not too difficult.