Column addition and subtraction

For bigger numbers we line up the digits in columns and add or subtract one column at a time, starting with the ones. When a column adds up to 10 or more, we carry; when the top digit is too small, we exchange.

Key facts

  • Line up ones under ones, tens under tens.
  • Start on the right, with the ones.
  • Adding: if a column makes 10 or more, write the ones digit and carry the ten.
  • Subtracting: if the top digit is smaller, exchange 1 from the next column (1 ten = 10 ones).

Worked examples

Example 1

Work out 467 + 285.

  1. Ones: 7 + 5 = 12. Write 2, carry 1.
  2. Tens: 6 + 8 + 1 = 15. Write 5, carry 1.
  3. Hundreds: 4 + 2 + 1 = 7. 467 + 285 = 752

Answer: 752

Example 2

Work out 503 − 268.

  1. Ones: 3 is less than 8. There are no tens, so exchange from the hundreds: 5 hundreds become 4 hundreds and 10 tens.
  2. Now exchange a ten: 9 tens and 13 ones. 13 − 8 = 5
  3. Tens: 9 − 6 = 3. Hundreds: 4 − 2 = 2. 503 − 268 = 235

Answer: 235