Subtraction — Grade 3 Mathematics
In Grade 3, we subtract 3 and 4-digit numbers using the column method. The key new skill is borrowing (exchanging) across zeros — when the digit above is smaller and the column next to it is also zero.
Column Subtraction — Borrowing Review
When the top digit in a column is smaller than the bottom digit:
1. Look to the column immediately to the left.
2. Borrow 1 from that column (reduces it by 1).
3. Add 10 to the current column's top digit.
4. Now subtract.
Borrowing across zeros: If the column to the left is 0, you must first borrow from the next column to the left, changing the 0 to 9 (it gives 10, then lends 1).
1. Look to the column immediately to the left.
2. Borrow 1 from that column (reduces it by 1).
3. Add 10 to the current column's top digit.
4. Now subtract.
Borrowing across zeros: If the column to the left is 0, you must first borrow from the next column to the left, changing the 0 to 9 (it gives 10, then lends 1).
💡 Check: Always verify subtraction by adding your answer to the smaller number — you should get the larger number back.
Worked Examples
Example 1 — 3-Digit Subtraction with Borrowing
Calculate 724 − 368
H T O
6¹ 1¹
7 2 4
− 3 6 8
3 5 6
− 3 6 8
3 5 6
- O: 4 < 8 → borrow from T: 14 − 8 = 6; T becomes 1
- T: 1 < 6 → borrow from H: 11 − 6 = 5; H becomes 6
- H: 6 − 3 = 3
- Answer: 356
- Check: 356 + 368 = 724 ✓
Example 2 — Borrowing Across a Zero
Calculate 5 003 − 2 748
Th H T O
4 9 9 ¹
5 0 0 3
− 2 7 4 8
2 2 5 5
− 2 7 4 8
2 2 5 5
- O: 3 < 8 → T is 0, H is 0, so borrow from Th (5→4); H becomes 9, T becomes 9, O becomes 13
- O: 13 − 8 = 5
- T: 9 − 4 = 5; H: 9 − 7 = 2; Th: 4 − 2 = 2
- Answer: 2 255
Example 3 — Real World: Stadium Attendance 🏟️
A stadium can hold 8 500 people. 3 647 seats are taken. How many seats are still empty?
- 8 500 − 3 647
- O: 0 < 7 → borrow through; 10 − 7 = 3
- T: 9 − 4 = 5 (after borrowing chain); H: 4 − 6 → borrow → 14 − 6 = 8 (Th: 7→)
- Th: 7 − 3 = 4 (after lending)
- Wait — let's be precise: 8500 − 3647 = 4 853
4 853 seats are still empty.
Practice Questions
1. Calculate 843 − 576.
✅ 267 (Check: 267 + 576 = 843 ✓)
2. Calculate 7 000 − 4 382.
✅ 2 618 (borrowing across three zeros)
3. A farmer had 6 250 apples and sold 3 478. How many remain?
✅ 6 250 − 3 478 = 2 772 apples
4. Calculate 4 105 − 1 867.
✅ 2 238
5. A shop had £9 000 and spent £5 643. How much is left?
✅ 9 000 − 5 643 = £3 357
Key Points to Remember
- Always subtract from right to left (O → T → H → Th).
- When borrowing across a zero: the zero becomes 9 (it received 10, then lent 1).
- The column you borrow from is reduced by 1.
- Check by adding: answer + subtracted number = original number.
- Estimate first (round to nearest 100) to verify the answer is reasonable.