During the early years children are not expected to employ written methods to subtract numbers. The aim at this stage is to use mental methods and become really efficient with this. However, the time comes when they must be taught one efficient method of subtraction.
There are three essential skills children should have before embarking on the standard written method:
a. know, off by heart, all addition and subtraction facts to 20
b. be able to subtract multiples of 10 (such as 150 – 60)
c. partition 2-digit and 3-digit numbers into multiples of one hundred, ten and one in different ways (For example partition 83 into 80 and 3 or 70 and 13).
When these skills have been securely grasped it is time to move towards the standard method, which is usually known as decomposition. We have a number of worksheets which explain this method and give practice with it. They can be found in our Four Rules section under subtraction.