Multi Digit Addition with Regrouping
When adding big numbers, sometimes a column adds to 10 or more. Thats when you REGROUP (also called carrying). Example: 47 + 35. Ones column: 7 + 5 = 12. Write 2, carry the 1. Tens column: 4 + 3 + 1 (carried) = 8. Answer: 82.
The Core Idea
Regrouping happens when a column total is 10 or more. You keep the ones digit, carry the tens digit to the next column. This works because 12 really is 1 ten + 2 ones. You are just writing it across the columns. Regrouping makes big addition work.
Example
256 + 178. Ones: 6 + 8 = 14. Write 4, carry 1. Tens: 5 + 7 + 1 = 13. Write 3, carry 1. Hundreds: 2 + 1 + 1 = 4. Answer: 434. Always line up digits by place value before you start.
What is 48 + 27?
Going Deeper
Regrouping is the same idea as place value. When you write the number 15, you are saying "1 ten and 5 ones." When you regroup during addition, you are just moving a ten to the tens column. Once you see this, regrouping stops feeling mysterious.
Practice Four
No Regrouping
In 156 + 278, what does the tens column sum to?
Is regrouping the same as carrying?
Want to keep learning?
Sign up for free to access the full curriculum — all subjects, all ages.
Start Learning Free