This activity is about working out the difference of two square numbers.

We use the fact that a² - b² factorises to (a + b) (a - b)

Example

Work out the difference of  these two squares:

485² - 483²

Answer

We need to work out (485 + 483) (485 - 483)

Notice that the first bracket equals 968 and that the second bracket equals 2

So this is 968 x 2 = 1,936

Being able to find the difference between two squares in this way can sometimes make it possible to do the calculation without the use of a calculator!

Let's have a go at some questions.