Question Video: Converting and Comparing between Lengths Mathematics

A red car is 411 centimeters long, a blue car is 500 centimeters long, and a black car is 3 meters long. Which car is the longest?

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Video Transcript

A red car is 411 centimeters long, a blue car is 500 centimeters long, and a black car is three meters long. Which car is the longest?

In this question, we need to compare the lengths of three cars. Let’s have a look at the measurements: 411 centimeters, 500 centimeters, three meters. What do you notice about these measurements? They’re not all measured in the same unit, are they? We’ve got two measurements in centimeters and one in meters. This means that we can’t just compare the numbers and look at them and see which one is largest.

Instead, we’re going to have to convert the measurements so that they’re all in the same unit of measurement. Should we change them all into meters or centimeters? It doesn’t matter which we choose, but with questions like this, we need to use a bit of common sense. Two of our measurements are already in centimeters, so the quickest thing to do would be to change the one that’s in meters into centimeters, and then they’re all in centimeters. We know that one meter is the same as 100 centimeters, and so three meters is the same as three lots of 100 centimeters or 300 centimeters.

Now that all our measurements are in centimeters, we could show them all on a number line. A red car is 411 centimeters. That’s about here on the number line. A blue car is 500 centimeters long. And although we said a black car was three meters, we worked out this was exactly the same as 300 centimeters. We made sure all our measurements were in the same unit so that we could then compare them. The longest of the three cars is the blue car.

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