| Operation | Key Rule | Example | Common Error |
|---|---|---|---|
| Addition | Line up decimal points | 12.3 + 5.67 = 17.97 | Not aligning: 12.3 + 5.67 ≠ 17.10 |
| Subtraction | Line up decimal points | 15.2 - 3.45 = 11.75 | Forgetting to borrow |
| Multiplication | Count total decimal places | 2.3 × 1.5 = 3.45 | Wrong decimal position |
| Division | Move decimal to make divisor whole | 6.3 ÷ 0.7 = 63 ÷ 7 = 9 | Not moving both decimals |
This key facts covers Operations with Decimals within Integers & Decimals for GCSE Mathematics. Revise Integers & Decimals in Number for GCSE Mathematics with 14 exam-style questions and 22 flashcards. This topic appears regularly enough that it should still be part of a steady revision cycle. It is section 3 of 13 in this topic. Use this key facts to connect the idea to the wider topic before moving on to questions and flashcards.
Practice questions for Integers & Decimals
What is the value of the digit 4 in the number 12.345?
Explain how to multiply two decimal numbers without a calculator.
Quick recall flashcards
Money calculation
£4.25 + £12.30 + £8.75
Line up decimals:
4.25
12.30
+ 8.75
------
25.30
Answer: £25.30
What is a decimal?
A number with a decimal point showing parts of a whole. The digits after the point represent tenths, hundredths, thousandths, etc.