# Year 3 Mental Arithmetic: Sets 21 and 22

Here we have the next two sets of questions in the Year 3 Mental Arithmetic series. This week the questions concentrate on using the vocabulary of addition and subtraction, including:

What is the sum of….?

What is the total of….?

What must I add to …. to make ….?

How many more than … is …?

How many less than … is …?

It is very useful to spend some time on asking children how they approach these questions, ‘in their heads’. For example:

‘What must I add to 7 to make 20?’ can be approached in several ways.

One way is to add on 3 to make 10 and then 10 more to make 20.

Another way is to add 10 and then count on 3.

A further method would be to take 10 from 20 and then count back 3 more.

By asking children to explain their methods it makes them think about what they have done and they will often see that there is a more efficient method than the one they used. The ultimate aim of this is to develop quick and efficient methods which produce correct answers.

Year 3 Mental Arithmetic: Sets_21 and 22