Adding 3-digit numbers with regrouping is one of the foundational computation skills in Grade 3 mathematics. It requires students to understand place value deeply — not just to follow a procedure, but to understand why the procedure works. Students who master 3-digit addition with regrouping carry that conceptual foundation into multi-digit multiplication, fraction operations, and eventually algebra.
This worksheet-style post explains the regrouping process step by step, then provides 20 practice problems with a complete answer key.
Understanding Regrouping: Place Value First
Before looking at a standard algorithm, it helps to understand regrouping in terms of place value. When you add two numbers and the result in a column is 10 or more, you regroup: carry the tens digit into the next column to the left.
Think of it this way: 10 ones = 1 ten. 10 tens = 1 hundred. Regrouping is simply trading smaller units for larger ones.
Step-by-Step Example: No Regrouping
3 4 2
+ 1 5 6
-------
4 9 8
Steps:
1. Add the ones: 2 + 6 = 8. Write 8 in the ones place.
2. Add the tens: 4 + 5 = 9. Write 9 in the tens place.
3. Add the hundreds: 3 + 1 = 4. Write 4 in the hundreds place.
Answer: 498.
Step-by-Step Example: Regrouping in the Ones Place
2 4 7
+ 1 3 6
-------
Steps:
1. Add the ones: 7 + 6 = 13. Write 3 in the ones place and carry 1 to the tens.
2. Add the tens: 4 + 3 + 1 (carried) = 8. Write 8 in the tens place.
3. Add the hundreds: 2 + 1 = 3. Write 3 in the hundreds place.
Answer: 383.
Step-by-Step Example: Regrouping in Both Columns
3 7 8
+ 4 6 5
-------
Steps:
1. Add the ones: 8 + 5 = 13. Write 3 in the ones place, carry 1 to tens.
2. Add the tens: 7 + 6 + 1 = 14. Write 4 in the tens place, carry 1 to hundreds.
3. Add the hundreds: 3 + 4 + 1 = 8. Write 8 in the hundreds place.
Answer: 843.
Practice Problems
Set A: No Regrouping
1. 234 + 152 = ___
2. 411 + 376 = ___
3. 520 + 245 = ___
4. 163 + 204 = ___
5. 300 + 489 = ___
Set B: Regrouping in the Ones Place Only
6. 245 + 138 = ___
7. 367 + 126 = ___
8. 419 + 254 = ___
9. 538 + 215 = ___
10. 623 + 149 = ___
Set C: Regrouping in the Tens Place Only
11. 362 + 191 = ___
12. 480 + 250 = ___
13. 271 + 183 = ___
14. 154 + 292 = ___
15. 463 + 283 = ___
Set D: Regrouping in Both Places
16. 386 + 247 = ___
17. 475 + 358 = ___
18. 563 + 278 = ___
19. 694 + 178 = ___
20. 787 + 145 = ___
Word Problems
21. A library has 348 books in the fiction section and 265 books in the nonfiction section. How many books are there in all?
22. At a school fair, 457 tickets were sold on Friday and 386 were sold on Saturday. What was the total number of tickets sold?
23. A farmer collected 275 apples on Monday and 368 apples on Tuesday. How many apples did he collect in two days?
Answer Key
Set A: 1) 386 2) 787 3) 765 4) 367 5) 789
Set B: 6) 383 7) 493 8) 673 9) 753 10) 772
Set C: 11) 553 12) 730 13) 454 14) 446 15) 746
Set D: 16) 633 17) 833 18) 841 19) 872 20) 932
Word problems: 21) 613 books 22) 843 tickets 23) 643 apples
Teaching Tips for Regrouping
- Use base-10 blocks first: Before introducing the written algorithm, let students physically trade 10 ones for 1 tens block and 10 tens for 1 hundreds block. This makes “carrying” conceptually clear, not just procedural.
- Say the regrouping out loud: Ask students to narrate each step as they write it: “8 plus 7 is 15. I write 5 and carry the 1.” Talking through the process reduces careless errors and strengthens understanding.
- Grid paper prevents alignment errors: Many regrouping mistakes come from students misaligning columns. Using grid paper or pre-formatted worksheets keeps digits in the correct place-value column.
- Check with estimation: Before calculating exactly, ask: “About how big should the answer be?” For 378 + 465, a student who rounds to 400 + 500 = 900 knows the answer should be close to 900 — and can immediately tell if they accidentally got 743 (too small) or 9,430 (too large).
Grade 3 Math Resources from ViewMath
ViewMath offers Grade 3 math workbooks and practice test books with topic-specific practice sets, including a dedicated section on addition and subtraction with regrouping. All books include complete answer keys. Explore the full Grade 3 collection in the sidebar.
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