Subtraction with borrowing across zeros, explained for parents
Why 503 − 267 trips kids up, and a clear way to teach borrowing (regrouping) across zeros, with worked examples and the mistakes to watch for.
Skill guide · Grades 2–4
Subtraction with borrowing (regrouping)
How borrowing in subtraction works, including across zeros, with a worked example, common mistakes and simple ways to practice at home.
What it is
Borrowing, also called regrouping or trading, is needed when the bottom digit in a column is bigger than the top digit. One ten from the next column is broken into ten ones, so the column has enough to subtract.
Zeros in the top number are where most kids get stuck, because there is nothing to borrow from in that column. The borrow has to come from further left, and each zero it passes becomes a 9.
A worked example
702 − 358 = 344
6
9
12
7
0
2
−
3
5
8
3
4
4
Every step, the way the pad explains it
- Subtract the ones: 2 is smaller than 8, so borrow. The tens is 0, so take 1 from the hundreds: 7 becomes 6, each 0 in between becomes 9, and 2 becomes 12. Now 12 − 8 = 4. Write 4.
- Subtract the tens (now 9 after borrowing): 9 − 5 = 4. Write 4.
- Subtract the hundreds (now 6 after borrowing): 6 − 3 = 3. Write 3.
- 1Ones: 2 − 8 needs a borrow, and the tens digit is 0.
- 2Borrow from the hundreds: 7 becomes 6, and the 0 tens become 10.
- 3Borrow one of those tens for the ones: 10 becomes 9, and the 2 becomes 12.
- 4Subtract right to left: 12 − 8 = 4, then 9 − 5 = 4, then 6 − 3 = 3.
- 5The answer is 702 − 358 = 344. Check by adding: 344 + 358 = 702.
Common mistakes
Taking the smaller digit from the bigger one in every column.
Ask which number we start with. It is always the top one.
Turning the 0 into 10 and leaving it there.
The 10 lends one to the column on its right, so it ends up as 9.
Forgetting to reduce the digit they borrowed from.
Cross it out and write the new digit above every time.
Borrowing when the top digit is already big enough.
Check each column first: is the top digit at least as big as the bottom one?
Grade range and practice
Usually taught in grades 2–4. Schools order topics a little differently, so your child’s class may meet it earlier or later.
- Work up a ladder: no zeros, a zero in the ones, a zero in the tens, then two zeros.
- Check every answer by adding it back to the bottom number.
- Use dimes and pennies to act out breaking a ten.
Read more on the blog
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