Column subtraction · Grade 3

In Grade 3 you learn: estimating to check an answer.

Column subtraction is a written method for subtracting numbers too big to do in your head. Line the numbers up by place value, subtract one column at a time from the ones, and exchange 1 from the next column when the top digit is smaller.

Key facts

  • Line up the digits by place value: ones under ones, tens under tens (and decimal points under each other).
  • Always start with the ones column, on the right.
  • Subtracting: if the top digit is smaller, exchange 1 from the next column (1 ten becomes 10 ones).
  • Check: answer + number taken away = the number you started with.
  • Estimate first by rounding each number; if your answer is far from the estimate, check your working.

Worked examples

Example 1

473 − 156

Answer: 317

Example 2

625 − 258

Answer: 367

Example 3

742 − 386

Answer: 356

Other years