Column subtraction – Year 3 maths lesson

For parents: how to use this lesson

You don't need to know this topic yourself. The lesson explains each step on screen, the way Mr Euclid, our Head of Maths, likes it: one tidy step at a time. Every answer is marked straight away with a worked explanation, so you never have to mark anything.

1. Read what your child will learn together.
2. Press Start the lesson below and sit with your child for the teaching and the worked examples (about 19 minutes).
3. Let them do the practice on their own. They choose Getting started, On track or Challenge – start on On track and move up after a few right in a row.
4. Finish with the exit ticket and the talk question: “Explain what happens when you need to exchange from a zero.”
5. Later that day or the next day: the homework (15 minutes), then a practice test.

Watch out for

• Taking the smaller digit from the bigger one whatever the order (e.g. 2 − 7 written as 5). Read each column aloud as "top take away bottom"; if you cannot, exchange.
• Forgetting to reduce the column you exchanged from. Always cross out and rewrite the digit as soon as you exchange.
• Getting stuck at a zero. Show 400 − 1 with base 10 blocks: a hundred is exchanged for 10 tens, then a ten for 10 ones.

Miss Hypatia's tip for home: Work out change or the difference between two heights, then check by adding.