Line the numbers up with the bigger number on top. Start with the ones. Take the bottom digit away from the top digit in each column.
If the top digit is smaller, exchange: take one from the next column on the left and add ten to this column. For 642 − 317: 2 − 7 does not work, so exchange a ten. 12 − 7 = 5, then 3 − 1 = 2, then 6 − 3 = 3. The answer is 325.
Worked example
Work out 534 − 261
- Ones: 4 − 1 = 3.
- Tens: 3 − 6 does not work, so exchange a hundred: 13 − 6 = 7. Hundreds: 4 − 2 = 2.
Answer:273
Key words
- exchange
- swap one bigger unit for ten smaller ones
- top number
- the number you take away from
- check
- add the answer to the bottom number
Practise this
New questions every time.
Common Core-referenced: 2.NBT.B.7