Addition with regrouping: how to help your child practice

What is addition with regrouping?

Regrouping means trading 10 ones for 1 ten (or 10 tens for 1 hundred) when a column gets too full. In 47 + 38, the ones column is 7 + 8 = 15. Fifteen ones is the same as 1 ten and 5 ones, so you write the 5 in the ones place and carry the 1 ten over to the tens column.

That's all "carrying" is: keeping each place to a single digit by bundling groups of ten. Kids who understand the bundle, not just the little 1 on top, make far fewer mistakes when the numbers get bigger.

In most US schools, 2nd graders add 2-digit numbers with regrouping (and start on 3-digit sums), and 3rd graders are expected to add fluently within 1,000. Regrouping in addition is the mirror image of borrowing in subtraction, covered in the addition and subtraction topic guide. See the addition and subtraction topic guide for the bigger picture.

How do you add with regrouping, step by step?

Use the same four steps every time, starting on the right:

1. Line up the numbers by place. Ones under ones, tens under tens. For 47 + 38, the 7 sits over the 8.
2. Add the ones. 7 + 8 = 15.
3. If the ones add up to 10 or more, regroup. Write the 5 in the ones place and carry the 1 ten to the top of the tens column.
4. Add the tens, including the carried ten. 4 + 3 + 1 = 8. The answer is 85.

For 3-digit numbers, keep going left. In 258 + 167: ones 8 + 7 = 15 (write 5, carry 1), tens 5 + 6 + 1 = 12 (write 2, carry 1), hundreds 2 + 1 + 1 = 4. The answer is 425.

Finish with a quick estimate: 47 is about 50 and 38 is about 40, so the answer should be near 90. An answer of 75 or 715 is a sign something went wrong.

What addition with regrouping mistakes do kids make most?

Forgetting the carried ten

A child adds 47 + 38, writes the 5, then adds 4 + 3 = 7 and gets 75. The ten from 7 + 8 = 15 disappeared. Have them write the little 1 at the top of the tens column before doing anything else, and touch it as they add the tens.

Writing the whole ones sum

A child writes all of 15 under the ones column and gets 715 for 47 + 38. Only one digit fits in each place. Ask, "Can 15 fit in the ones place?" and show 15 pennies turning into 1 dime and 5 pennies.

Lining up the numbers wrong

For 64 + 9, a child puts the 9 under the 6 and gets 154 instead of 73. Turn lined paper sideways so the lines make columns, or label the columns T and O before writing the numbers.

How can you practice addition with regrouping at home in 10 minutes?

A few mixed problems a day beat a page of 30 identical ones.

• Minutes 1–3: build one. Use dimes and pennies (or bundles of 10 straws). Show 27 + 15 with real objects, then trade 10 pennies for a dime. Your child sees why the 1 gets carried: 4 dimes and 2 pennies, or 42.
• Minutes 4–8: five mixed problems. One with no regrouping (32 + 45), three that need it (39 + 26, 58 + 34, 66 + 17), and one 3-digit problem for 3rd graders (146 + 278).
• Minutes 9–10: check one out loud. Have your child estimate first, then explain where the carried 1 came from in one of the problems.

Repeat a few times over the week with new numbers, so your child practices the regrouping itself rather than remembering answers.

How can Easy Twin help with addition with regrouping?

Scan your child's addition worksheet and Easy Twin makes a twin with the same kinds of questions and new numbers, so practice matches what the class is doing this week. Every question comes with two hints and worked steps, visuals like number lines and tables are redrawn with new data, and your child can play the twin as a quest or you can print it with an answer key.

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