Decimal Subtraction
Subtracting decimals follows the same column method as subtracting whole numbers. The key rule: align the decimal points before you begin.
The Golden Rule – Align the Decimal Point
8.4 − 3.57 → write as 8.40 − 3.57, align points, then subtract
Padding with Zeros
Add trailing zeros so both numbers have the same number of decimal places.
| Original | Padded |
|---|---|
| 7.5 − 2.38 | 7.50 − 2.38 |
| 5 − 1.234 | 5.000 − 1.234 |
Worked Examples
Easy
9.7 − 4.3: ones 9−4=5, tenths 7−3=4. Answer: 5.4
Medium – With Borrowing
6.32 − 2.87: hundredths 2−7 borrow; 12−7=5. Tenths 2−8 borrow; 12−8=4 (adjusted). Ones 5−2=3. Answer: 3.45
Advanced
12.5 − 8.375: pad 12.500 − 8.375. Work right to left with borrowing. Answer: 4.125
Real-Life Applications
- Calculating change: £10 − £3.47 = £6.53
- Comparing measurements: 2.85 m − 1.6 m = 1.25 m
- Tracking weight loss or gain in health.
Key Takeaways
- Always align decimal points before subtracting.
- Pad with trailing zeros where needed.
- Borrowing works exactly as with whole numbers.
- The decimal point in the answer sits directly below those in the calculation.
Practice Questions
- Calculate 7.8 − 3.4.
- Calculate 5.62 − 2.38.
- Subtract 4.7 from 10.
- A rope is 6.5 m long; 2.85 m is cut off. How much remains?
- Calculate 15 − 8.375.