Video: Finding the Difference between Two Lengths in Centimeters

How much longer is the bigger pencil than the smaller one?

02:37

Video Transcript

How much longer is the bigger pencil than the smaller one?

Our picture shows two pencils, a red one and a yellow one. Now, if we look at how these pencils have been lined up, we can see that the pointed end, which is the end that we write with, are both level with each other. This makes it easier for us to measure and also to see which pencil is longer. If we look at the other end, which is the end with the rubber, we can see some dotted lines which clearly show us the red pencil is the bigger.

But our question wants us to find the difference between these two lengths because it asked us, how much longer is the bigger pencil than the smaller one? And to find out this, the first thing we’re going to have to do is to measure these pencils.

Let’s start with the red one. We can see that the pointed end of the pencil is level with the number zero on our ruler. And if we look carefully, we can see the letters cm. Which means that we’re measuring in centimeters. And the red pencil goes all the way from zero to the number 19 on our ruler. It’s 19 centimeters long. Now, let’s measure our yellow pencil. Again, we’re starting measuring from zero. But this time, the pencil only goes as far as the number 16. It’s 16 centimeters long.

Now, we can use what we’ve found to answer the question. How much longer is 19 centimeters than 16 centimeters? One way of finding the answer is to use our ruler as a sort of number track or number line. All we have to do is to count how many centimeters there are in between our two lengths. To get from 19 to 16, we can count one, two, three centimeters. It looks like the bigger pencil is three centimeters longer than the smaller one.

Another way we can find the difference is to subtract. So, we start with the longer length, which is 19, and we’re going to take away 16. So, we’re going to take away one, two, three, four, five, six, seven, eight, nine, 10, 11, 12, 13, 14, 15, 16. We’re left with three.

We found the same answer in two different ways. The bigger pencil is three centimeters longer than the smaller one.

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