We explain what the column method is, how it is set out and why it is an efficient method for working out addition and subtraction.
Column method of addition and subtraction is the method where numbers are 'carried' and 'borrowed'. It is set out like this:
This is a quick and efficient method for working out addition and subtraction, but the downside is that a child could use this method without having any awareness of place value (that is: they would not understand that the 3 in the above number is not 3, but in fact 30). It also means that they are not learning to add and subtract multiples of 10 or 100 (for example: 30 + 90, 120 - 50 etc). In order to help children understand these concepts, teachers often use partitioning for addition and a number line for subtraction.
Alternatively, they may use a combination of the column method and partitioning to add, which would look like this:
Once children are aware of place value and also have the ability to mentally add and subtract multiples of ten and one hundred, they would probably be encouraged to move onto the column method involving 'carrying' numbers, as this is the quickest method.