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Estimating Sums Worksheets for 3rd Grade

Round each number first, then add to estimate a sum. 15 free printable worksheets, each with an answer key.

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Free Estimating Sums Worksheets

Click a worksheet to open the PDF, or grab the matching answer key. Every sheet prints on one page.

Estimating Sums: what children learn

Estimating a sum means rounding each number to a friendly ten or hundred and then adding. It lets children check whether an exact answer makes sense.

Estimating Sums: worked example

Round to the nearest 10. About how much is 38 + 54? 90

38 rounds to 40 and 54 rounds to 50. Then 40 + 50 = 90.

Estimating Sums: a common mistake to watch for

Kids sometimes add the real numbers first and then round the total, which can give a different estimate.

Estimating Sums: how to help at home or in class

Flip through a store flyer with whole-dollar prices and ask whether two items together cost more or less than 100 dollars. Your child rounds each price to the nearest ten, adds, and decides. Afterwards, find the exact total and compare the two. Seeing how close an estimate lands builds trust in the method. When estimates are reliably near the exact sums, use the same rounding trick for differences.

What is on these Estimating Sums worksheets

This set has 15 different worksheets for 3rd grade, with 8 questions on each and a matching answer key for every sheet. The instruction printed on each worksheet is: “Round each number first. Then add the rounded numbers.”

Example questions like the ones on these worksheets, with their answers:

  • Round to the nearest 10. About how much is 47 + 29?80
  • Round to the nearest 10. About how much is 21 + 26?50
  • Round to the nearest 100. About how much is 541 + 271?800
  • Round to the nearest 10. About how much is 69 + 13?80
  • Round to the nearest 10. About how much is 52 + 99?150
  • Round to the nearest 10. About how much is 75 + 19?100
  • Round to the nearest 10. About how much is 97 + 96?200
  • Round to the nearest 10. About how much is 115 + 556?680

Every answer on every sheet is checked by a separate program before the worksheet is published. How we check answers

Related Place Value & Rounding worksheets for 3rd grade

Rounding to the Nearest 10
Round numbers up to 999 to the nearest ten, including numbers that end in 5.
Rounding to the Nearest 100
Round three-digit numbers to the nearest hundred, including numbers that end in 50.
Rounding to the Nearest 10 or 100
Round numbers to the nearest 10 or the nearest 100, as each question says.
Estimating Differences
Round each number first, then subtract to estimate a difference.
All Place Value & Rounding worksheets
See every place value & rounding topic for 3rd grade