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.
Explore this idea with maths tools
Jump on a number line
2 + 3 = 5
Positive jumps go right. Negative jumps go left. Zero stays in the middle.
Words to know
- regroup
- change one ten into ten ones (or one hundred into ten tens)
- difference
- the answer to a subtraction
Worked examples
52 − 27 = ?
- 1.2 − 7 can't be done: regroup 1 ten, so 52 is 4 tens and 12 ones.
- 2.Ones: 12 − 7 = 5. Tens: 4 − 2 = 2.
= 25
734 − 258 = ?
- 1.Regroup twice: 734 becomes 6 hundreds, 12 tens and 14 ones.
- 2.14 − 8 = 6, 12 − 5 = 7, 6 − 2 = 4.
= 476
503 − 278 = ?
- 1.No tens to regroup, so regroup a hundred: 5 hundreds becomes 4 hundreds and 10 tens.
- 2.Then regroup a ten: 9 tens and 13 ones.
- 3.13 − 8 = 5, 9 − 7 = 2, 4 − 2 = 2.
= 225
For parents
Method: Column subtraction (decomposition)
What to say: Is the top digit big enough? Where can you regroup from? What does that digit become?
Common mistakes:
- In each column takes the smaller digit from the larger, whichever is on top.
- Adds ten to the top digit when regrouping but does not take one away from the next column.
- Writes 0 in a column when the top digit is smaller than the bottom digit.
- When regrouping across a zero, changes the zero to 10 but does not then take one ten from it (it should end as 9).
- Regroups from the next non-zero digit but leaves the zero in between unchanged.
- Lines the numbers up on the left instead of by place value when they have different numbers of digits.