In this Maths article, learn how to recognise and do sums with numbers up to a million. ... When working with big numbers, place value grids are a great way to see how the number is made. Back to top.

I can do this in my head using place value. 15.35 seconds is made up of 1 ten, 5 ones, 3 tenths and 5 hundredths. So I need to work out the difference between 15.35 and 16.44.