# Video: KS1-M16 • Paper 2 • Question 11

There were 20 balloons. 7 balloons flew away. How many balloons are left?

02:17

### Video Transcript

There were 20 balloons. Seven balloons flew away. How many balloons are left?

We’re told that there were 20 balloons. This is the number that we begin with. But we’re then told that seven balloons flew away. And we’re asked to calculate the number of balloons that are left. In other words, what number is seven less than 20? We need to work out 20 take away seven to find the answer. One way we can find the answer is to think of the number 20 as being worth two 10s. If we take away seven, one of those 10s is going to be broken up.

We can show this using ten frames. Here are our two 10s. Now, if we take away seven from these two 10s, one of our 10s, as we’ve said, is going to be broken up. So if we subtract seven from this 10, what are we going to be left with. We’re going to be left with the number that pairs with seven to make 10. Seven plus three makes 10. So we’re left with one 10 and 3 ones. 20 take away seven equals 13. There’re 13 balloons left.

Let’s check that our answer is correct by seeing whether 13 and seven make 20. We can start with 13 and then add one, two, three, four, five, six, seven. The difference between 13 and 20 is seven. And so 20 take away seven equals 13. There were 20 balloons. Seven balloons flew away. And now, there are 13 balloons left.