Video: Estimating the Difference between Two Three-Digit Numbers by Rounding to the Nearest Hundred

Look at how Victoria rounded to estimate this difference. Round the numbers in this calculation to the nearest hundred. 372 − 211 = _

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Video Transcript

Look at how Victoria rounded to estimate this difference: 432 take away 279. She rounded 432 to the nearest 100, 400; 279 to the nearest 100, 300. 400 take away 300 equals 100. Round the numbers in this calculation to the nearest 100. 372 take away 211.

First, we need to round 372 to the nearest 100. 372 is between 300 and 400. 350 is halfway between 300 and 400. 372 would be roughly halfway between 350 and 400. The nearest 100 to 372 is 400. Next, we need to round 211 to the nearest 100. 211 is between 200 and 300. It would go roughly here on the number line. This means that 211’s nearest 100 is 200.

Now that we’ve rounded both of our numbers to the nearest 100, we can calculate our estimate. 400 take away 200 is 200. But the question doesn’t ask us to calculate the estimate, just to round the numbers to the nearest 100. If we round the numbers in the calculation 372 take away 211 to the nearest 100, the estimate will be 400 take away 200.

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