The note
How schools teach it now
Built on column addition and subtraction. Schools say 'exchange' rather than 'borrow' (you exchange 1 ten for 10 ones). Children work column by column from the ones and check with the inverse operation.
5-minute kitchen-table activity
Write a sum from a receipt, cover two digits with coins and swap seats. Your child finds the hidden digits, then lifts the coins to check. Next, they set one for you.
Worked example
3☐6 + 25☐ = 611. Find the missing digits.
- Ones: 6 + ☐ must end in 1, so ☐ = 5 (6 + 5 = 11, carry 1).
- Tens: ☐ + 5 + 1 must end in 1, so ☐ = 5 (5 + 5 + 1 = 11, carry 1).
- Hundreds: 3 + 2 + 1 = 6. It works.
Answer: 356 + 255 = 611
Common mistakes to watch for
- Forgetting the 1 carried into the next column.
- Starting from the left instead of the ones column.
- Not checking that the finished sum really works.
Encouragement
- Try saying
- “Start with the ones: what must that box be?”
- Rather than
- “Just try numbers until one works.”