Video: Rounding Whole Numbers to the Nearest 10 Using a Number Line

To round 3-digit numbers to the nearest ten, use a number line. Think about the number 437. Which two multiples of 10 is 437 between? Hint: We use the digit in the tens place to guide us. What is 437 rounded to the nearest 10? Hint: Think about which side of the midpoint 437 will be on.

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Video Transcript

To round three-digit numbers to the nearest 10, use a number line. Think about the number 437. We can add in the midpoint to help us. Which two multiples of 10 is 437 between? Hint: We use the digit in the tens place to guide us. What is 437 rounded to the nearest 10? Hint: Think about which side of the midpoint 437 will be on.

This problem takes us through several steps. And it teaches us along the way. It’s showing us how to round three-digit numbers to the nearest 10. And the way we’re shown how to do this is using a number line. So even though there are two parts to this question that need answering, there are still plenty of explanations and hints to help us. It really is a problem that’s been written to teach us step by step. And our first step is to think about the number 437. We can then see part of a number line has been drawn. We could sketch the same sort of thing for ourselves at the bottom.

The number line, and it seems to have two longer lines marked on it at either end. Normally on the number line, we’ll expect these to be multiples of 10. But the label also tells us that we can add in the midpoint to help us. So because it’s going to be helpful, let’s draw in our midpoint. First part to our problem asks us, which two multiples of 10 is 437 between? In other words, what it’s asking us is what is this number here and what is this number here. And we’re given a hint. We use the digit in the tens place to guide us.

We know that the number 437 is made up of four hundreds, three tens, and seven ones. The digit in the tens place is the digit three. This tells us that the multiple of 10 less than our number will be 430. In other words, four hundreds, three tens, and zero ones. And to find the multiple of 10 greater than our number, we need to add one to this tens digit. So instead of 430, we have 440. The two multiples of 10 that 437 is between are 430 and 440.

In the final part of the problem, we need to use what we’ve worked out already to round 437 to the nearest 10. Is it going to be rounded down to 430 or up to 440? Again, we’re given another hint to help us. Think about which side of the midpoint 437 will be on. The midpoint is halfway between 430 and 440. This is 435. Notice how the hundreds and the tens digits are the same as our number, but the ones digit is less. Where would we expect 437 to be? To the left of 435 or somewhere to the right? Well, as we’ve noticed already, seven ones are greater than five ones. So we know that 437 is going to be somewhere to the right of 435.

The nearest multiple of 10 to 437 then will be 440. We followed the steps and used a number line to round 437 to the nearest 10. First, we found the two multiples of 10 that 437 was in between. And they are 430 and 440. We decided that the midpoint was 435. And then we thought about which side of the midpoint 437 was going to be on. 437, rounded to the nearest 10, is 440.

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