There are many simple facts and techniques which help children become fast and accurate with mental arithmetic. One of them is to know, off by heart, pairs of numbers that make 100.Knowing these facts comes with practice, but even if they are not known there are still ways to respond really quickly. Realising that the two tens digits will add up to 9 and the two ones digits will add up to 10 can make finding the answers really quick – try it out on our latest, ‘Pairs to make 100’ worksheets.Go to Year 3 Addition