Looking at subtraction

The comparison structure

The key language to be developed in the comparison structure of subtraction includes: What is the difference? How many more? How many less (or fewer)? How many greater? How much smaller? The comparison structure namely refers to situations where subtraction is required to make a comparison between two quantities, for example how many more blue cubes are there than red cubes?

The calculation to be entered on a calculator would be 12 – 7. Subtraction of the smaller number from the greater enables us to determine the difference.  Or to find out how much greater or how much smaller one quantity is than the other.

There are endless contexts where pupils will meet subtraction in the comparison structure. Wherever two numbers occur we will find ourselves wanting to compare them, to determine the difference, or to find out how much smaller or greater one is than the other.

When comparing two quantities, A and B, use both forms of the question. For example, How much greater is A? How much smaller is B? How much longer is A? How much shorter is B? How much heavier is A? How much lighter is B? How much older is A? How much younger is B? How much later is A? How much earlier is B?

Because making comparisons is such a fundamental process, with so many practical and social applications, the ability to recognise this subtraction structure and the confidence to handle the associated language patterns are particularly important.