Addition and Subtraction with Regrouping for Grade 2

What Regrouping Means

Regrouping happens when the ones place needs to change. In addition, 10 ones can be grouped into 1 ten. In subtraction, 1 ten can be broken into 10 ones.

This works because place value tells us that 10 ones and 1 ten are worth the same amount.

Base-ten blocks, drawings of sticks and dots, or place-value charts can make this idea visible. Students should be able to point to a group of 10 ones and explain why it may be traded for 1 ten. They should also explain that when a ten is broken apart, the total amount stays the same even though the pieces look different.

Add by Making a New Ten

Try 27 + 15. Start with the ones: 7 + 5 = 12 ones. Regroup 10 of those ones as 1 new ten. Now you have 2 ones left? No. You have 12 ones, which is 1 ten and 2 ones.

Then add the tens: 2 tens + 1 ten + 1 regrouped ten = 4 tens. The answer is 42.

Students benefit from writing the equation vertically so the ones line up with ones and the tens line up with tens. They should say each step aloud: add the ones, rename 10 ones as 1 ten, write the 2 ones, then add the tens. Estimating first can also help them notice if an answer such as 402 or 24 does not make sense.

When students use drawings, they can circle 10 ones and trade that group for one ten stick. When they use the written algorithm, the small 1 written above the tens place should be connected back to that model. That small mark is not extra value. It shows the new ten that came from the 10 ones.

Subtract by Breaking a Ten

Try 43 - 18. You cannot take 8 ones away from 3 ones, so regroup 1 ten as 10 ones. Now 43 becomes 3 tens and 13 ones.

Subtract the ones first: 13 - 8 = 5. Then subtract the tens: 3 tens - 1 ten = 2 tens. The answer is 25.

This is a strong place to slow down and talk through the meaning. Students are not "borrowing" a mysterious 1. They are taking 1 ten from the tens place and renaming it as 10 ones. After regrouping, the tens digit becomes smaller because one group of ten was moved to the ones place. That place-value explanation makes subtraction steps more accurate and easier to remember.

It also helps to connect subtraction to checking. If students solve 43 - 18 = 25, they can check by adding 25 + 18 to see whether the total returns to 43. That inverse relationship between addition and subtraction gives them another way to notice mistakes in regrouping.

Use Regrouping in Word Problems

Regrouping shows up in story problems too. If a class has 36 markers and buys 27 more, students need to add across tens and ones. If 52 stickers are shared and 19 are used, students need to regroup to subtract.

Always decide whether the story is asking you to put together or take away first, then solve carefully.

Students should underline the important numbers, circle clue words only if they help, and retell the story in their own words before solving. After finding an answer, they should check whether it is reasonable. If 52 stickers were in the box to begin with, an answer larger than 52 would not make sense for the subtraction story. That final check builds number sense as well as accuracy.

A useful routine is write, solve, explain, and check. Students write an equation, solve with regrouping, explain what they traded in tens and ones, and check the answer with an estimate or inverse operation. That process makes regrouping feel like mathematical reasoning instead of a memorized sequence of marks.