Looking at addition

Commutative law of addition

The commutative property of addition is simply the fact that an addition can go both ways: 17 + 15 = 15 + 17, and so on. We can state the commutative law formally by the following generalisation, which is true whatever the numbers a and b.

a + b = b + a 5 + 6 = 6 + 5

In your teaching it is important to make explicit the commutative law of addition. Show them how to use it in addition calculations, particularly by starting with the bigger number when counting on. Explain that subtraction does not have this property.