Column subtraction · Year 3

In Year 3 you learn: column subtraction of 3-digit numbers and exchanging.

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.

Worked examples

Other years

• Column subtraction · Year 4
• Column subtraction · Year 5