operations · Year 3 · AC9M3N03
Column subtraction with regrouping
Write the bigger number on top, with ones under ones. Start with the ones. If the top digit is smaller than the bottom digit, don't swap them: regroup one ten from the next column into ten ones. Cross out that ten's digit and make it one less. If the next digit is 0, regroup from the place after it first, so the 0 becomes 10 and then 9.
Sample questions
81 − 18 = ?
- Regroup wherever the top digit is smaller. 81 becomes 7 tens, 11 ones.
- Subtract each column, starting with the ones: 11 − 8 = 3, 7 − 1 = 6.
- 81 − 18 = 63.
Answer: 63
82 − 48 = ?
- Regroup wherever the top digit is smaller. 82 becomes 7 tens, 12 ones.
- Subtract each column, starting with the ones: 12 − 8 = 4, 7 − 4 = 3.
- 82 − 48 = 34.
Answer: 34
62 − 18 = ?
- Regroup wherever the top digit is smaller. 62 becomes 5 tens, 12 ones.
- Subtract each column, starting with the ones: 12 − 8 = 4, 5 − 1 = 4.
- 62 − 18 = 44.
Answer: 44