2-Digit Addition with Regrouping (2nd Grade)

What is it?

Regrouping (some families call it carrying) is what you do when the ones add up to 10 or more. A digit can only go up to 9, so 10 ones are traded for 1 ten and moved to the tens place. The lesson shows base-ten blocks (green rods for tens, small cubes for ones) next to the written problem, so your child sees that the little 1 written above the tens is a real ten made from ten ones.

Step by step: 38 + 25

1. 38 is 3 tens and 8 ones. 25 is 2 tens and 5 ones.
2. Add the ones first: 8 ones + 5 ones = 13 ones.
3. 13 ones is more than 9, so trade 10 ones for 1 ten. 3 ones are left.
4. Add the tens: 3 tens + 2 tens + 1 more ten = 6 tens.
5. 6 tens and 3 ones make 63. So 38 + 25 = 63.

Common mistakes

• Writing 13 in the ones place (getting 513). Only 3 ones stay; the ten moves over.
• Forgetting to add the traded ten: 3 tens + 2 tens = 5 tens gives 53 instead of 63.
• Starting with the tens. Add the ones first, because they may make a new ten.

Your turn

The lesson ends with a problem to try. Pause and let your child work it out before you check.

What is 47 + 36?

Answer: 83. 7 + 6 = 13 ones, so trade 10 ones for a ten and keep 3 ones. Then 4 tens + 3 tens + 1 ten = 8 tens.

Practice at home

Use dimes for tens and pennies for ones. Build both numbers, put the pennies together, and when there are 10 or more, trade 10 pennies for a dime. Then write the same problem on paper and point out that the little 1 above the tens is the dime you traded.