### Video Transcript

Pick the number that is missing from the number line. 60000, 43000, or 55000.

There’re only two numbers that have been labelled on our number line, and they’re at either end. We have 40000 on the left and 70000 on the right. And halfway between, we have a missing number. We’re being asked to pick the number that’s missing from the number line and we’re given three possible choices. Is it 60000, 43000, or 55000?

To find the answer, we need to think about what each interval along the number line is worth because our missing number is only three intervals along from 40000. Each jump could be any amount. So, what can we use to help us? Well, there are several different strategies we could use. And they all involve looking at the final number, 70000, and using this to help us.

One method might be just to try different numbers. For example, if each jump is worth 1000, then our missing number would be 43000. And this is one of our possible answers. But if we counted on in thousands from 43000, we’re not going to get to 70000. Each interval is not worth 1000. So, we could keep on trying different numbers like this.

Another method we could use could be to count the number of jumps that we have between 40000 and 70000 and to use this to help. One, two, three, four, five, six. And we can see that our missing number is three jumps along. So, it’s halfway between 40000 and 70000. The difference between 40 and 70 is 30. So, the difference between 40000 and 70000 is 30000. There are six intervals. We know that 30 divided by six equals five, and so 30000 divided by six must equal 5000. Let’s try jumps of 5000 to see if this works.

We’ll start with 40000, 45000, 50000. This would make our number 55000. And this is one of our possible answers. Let’s keep counting and see if this works and takes us all the way to 70000. 60000, 65000, 70000. Each interval has a value of 5000. Our missing number is three intervals away from 40000. It’s also halfway between 50000 and 60000. The number that is missing from our number line is 55000.