So, KS3 Maths has made you familiar with square numbers and cube numbers. They are powers denoted by a 2 or a 3 above and to the right of another number. For example, 3 squared is 32 and 3 cubed is 33. But there is another side to squares and cubes - roots.
A number multiplied by itself creates its own square. The original number is called the square root of the new number. For example, the square root of 9 is 3 because 3 x 3 = 9. It's similar with cube roots. A number multiplied by itself twice creates a cube number. The original number is the cube root of this. For example, the cube root of 64 is 4 because 4 x 4 x 4 = 64. It's not easy to work out square or cube roots. It usually involves a great deal of trial and error - or a calculator!
It would be great if you could memorise the square and cube values of lower numbers. That would help you a lot but might take a considerable amount of time. In the meanwhile, try this quiz to get some practise with square and cube roots..