You are saving up your pocket money. Last week you had £2.45 and this week Grandad gave you £1.30 more. How much now? Lining numbers up in tidy columns makes big sums easy.
Why this matters: Column adding and subtracting helps you work out change in a shop, count how much sadaqah your family has collected, and check no money has gone missing.
The golden rule: line up the columns
Always put units under units, tens under tens, and hundreds under hundreds. Start from the right (the units).
346
+ 125
-----
Units: 6 + 5 = 11. Write 1, carry 1 ten.
Tens: 4 + 2 + 1 = 7.
Hundreds: 3 + 1 = 4.
Answer: 471
+ 125
-----
Units: 6 + 5 = 11. Write 1, carry 1 ten.
Tens: 4 + 2 + 1 = 7.
Hundreds: 3 + 1 = 4.
Answer: 471
Put these steps in order for column addition:
- Line up units under units, tens under tens
- Add the units column first
- Carry any extra ten into the tens column
- Add the tens, then the hundreds
Carrying (when a column goes over 9)
If a column adds up to 10 or more, write the units digit and carry the extra ten into the next column. That little carried 1 is like swapping ten pennies for one 10p coin.
Subtracting with exchanging (borrowing)
If the top digit is too small, exchange one from the next column along.
452
- 128
-----
Units: 2 - 8 won't work, so exchange 1 ten. Now 12 - 8 = 4. The 5 tens becomes 4 tens.
Tens: 4 - 2 = 2.
Hundreds: 4 - 1 = 3.
Answer: 324
- 128
-----
Units: 2 - 8 won't work, so exchange 1 ten. Now 12 - 8 = 4. The 5 tens becomes 4 tens.
Tens: 4 - 2 = 2.
Hundreds: 4 - 1 = 3.
Answer: 324
| Job | What you do |
|---|---|
| Adding | Carry extra tens forward |
| Subtracting | Exchange from the next column |
Try it: jump to add
Start at 8 and jump 7. Where do you land?