Grade 3 · Math · Lesson 7

Estimate Sums and Differences

Estimating means finding an answer that is close to the exact answer, but easier to calculate. To estimate sums and differences of 3-digit numbers, we round each number to the nearest hundred first, then add or subtract the rounded numbers.

What this lesson teaches

1Round each addend or subtrahend to the nearest hundred before computing
2Use rounded numbers to estimate sums and differences of 3-digit numbers
3Explain whether an estimate is an overestimate or an underestimate

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