The Primary Framework for Maths is very keen that children understand the relationships between numbers and operations. One of the most important is to realise that subtraction is the inverse of addition. So, once one fact is known, such as 6 + 8 = 14, other facts can immediately be derived, ie 8 + 6 = 14 14 - 6 = 8 and 14 - 8 = 6. This is not quite the same as knowing all of these 'off by heart', but it does mean that they can be worked out really quickly and it is speed, as well as accuracy, that we are all looking for. These pages take a quick look at this relationship, giving one fact and asking for the other three. Know other facts