Video: Writing the Decimal Numbers Marked on a Number Line

What decimals are marked on the number line?


Video Transcript

What decimals are marked on the number line?

At the moment, we can see that the only numbers that are actually labeled on the number line are three whole numbers. We have 18, then 19, and then finally 20. And we can also see that we have four decimal numbers that we need to complete. We know these are decimal numbers because they’re in-between the whole numbers. But how can we find out what each decimal’s worth?

We know that the distance between each of our whole numbers is one. In other words, from 18 to 19 is one whole, and from 19 to 20 is one whole too. But we can see that each whole has been split into 10 equal parts. So, each interval that’s marked with a notch is worth one-tenth. And if we think of this as a decimal, each notch is worth 0.1.

So, let’s find our first missing decimal by counting in tenths, 18.1, 18.2. And our first missing decimal is three-tenths along. It’s 18.3. The second decimal that’s marked on the number line is just before the number 19. Let’s count backwards in tenths to find this one, 18.9, 18.8. And our missing decimal is three-tenths less than 19. It’s 18.7.

The third decimal that’s marked along the line is one-tenth greater than 19. The decimal is 19.1. Finally, we can see that our last decimal is halfway between 19 and 20. How many tenths are the same as a half? We know five-tenths are worth the same as a half. So, halfway between 19 and 20 is 19.5. Our four missing numbers are 18.3, 18.7, 19.1, and finally 19.5.

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