Column addition and subtraction · Year 3

In Year 3 you learn: column addition and subtraction of 3-digit numbers; exchanging (carrying and borrowing).

Column addition and subtraction are written methods for numbers too big to do comfortably in your head. Lining the numbers up by place value means you only ever add or subtract single digits, carrying or exchanging tens when a column overflows or runs short.

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.
• Adding: if a column makes 10 or more, write the ones digit and carry 1 into the next column.
• 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 addition and subtraction · Year 4
• Column addition and subtraction · Year 5