Fractions and Decimals - Class 7 Mathematics (CBSE)
Based on the 2025-26 NCERT syllabus for Class 7 Mathematics. This chapter focuses on multiplication and division operations on fractions and decimals, building on the foundational concepts from Class 6.
1. Why this chapter matters
Fractions and decimals appear everywhere in daily life -- cooking measurements, money transactions, distances on maps, and exam percentages. Mastery of fraction and decimal operations is essential for higher topics like ratio, proportion, algebra, and data interpretation. CBSE exams allocate 8-12 marks to this chapter.
2. Multiplication of fractions
Multiplication of a fraction by a whole number
Multiply the numerator by the whole number; keep the denominator same.
(a/b) x c = (a x c) / b
Example: (3/7) x 5 = 15/7 = 2 1/7
Multiplication of a fraction by a fraction
Multiply numerators together and denominators together.
(a/b) x (c/d) = (a x c) / (b x d)
Example: (2/3) x (5/7) = 10/21
Product of proper fractions
Product of two proper fractions is less than each of the fractions.
- (1/2) x (3/4) = 3/8. Check: 3/8 < 1/2 and 3/8 < 3/4.
3. Division of fractions
Reciprocal
The reciprocal of a fraction a/b is b/a (where a and b are non-zero).
Division rule
Dividing by a fraction is the same as multiplying by its reciprocal.
(a/b) / (c/d) = (a/b) x (d/c) = (a x d) / (b x c)
Example: (5/6) / (2/3) = (5/6) x (3/2) = 15/12 = 5/4 = 1 1/4
Division of a whole number by a fraction
Example: 4 / (2/3) = 4 x (3/2) = 12/2 = 6
4. Multiplication of decimals
Multiplying a decimal by 10, 100, 1000
Shift the decimal point to the right by the number of zeros.
- 3.45 x 10 = 34.5
- 3.45 x 100 = 345
- 3.45 x 1000 = 3450
Multiplying two decimals
Multiply as whole numbers, then place decimal point. Total decimal places in product = sum of decimal places in factors.
Example: 2.5 x 1.4
- 25 x 14 = 350
- 2.5 has 1 decimal place, 1.4 has 1 decimal place. Total = 2 places.
- Answer: 3.50 or 3.5
5. Division of decimals
Dividing a decimal by a whole number
Divide as usual, keep decimal point aligned.
Example: 6.4 / 2 = 3.2
Dividing by 10, 100, 1000
Shift decimal point to the left.
Example: 45.6 / 100 = 0.456
Dividing a decimal by a decimal
Convert the divisor to a whole number by multiplying both dividend and divisor by 10, 100, or 1000.
Example: 4.8 / 1.2 = (4.8 x 10) / (1.2 x 10) = 48 / 12 = 4
6. Worked examples
Example 1: Multiply (3/5) x (10/9)
(3 x 10) / (5 x 9) = 30/45 = 2/3 (after simplification)
Example 2: Divide (7/12) / (14/15)
(7/12) x (15/14) = (7 x 15) / (12 x 14) = 105/168 = 5/8
Example 3: Multiply 0.75 x 0.6
75 x 6 = 450. Total decimal places = 2 + 1 = 3. Answer = 0.450 = 0.45
Example 4: A car travels 45.6 km in 3.8 litres of petrol. Find distance per litre.
Distance per litre = 45.6 / 3.8 = (45.6 x 10) / (3.8 x 10) = 456 / 38 = 12 km per litre
7. Common mistakes and how to fix them
| Mistake | Fix |
|---|---|
| Adding denominators during fraction multiplication | Multiply denominators too, don't add them |
| Forgetting to take reciprocal during division | (a/b) / (c/d) = (a/b) x (d/c), not (a/b) x (c/d) |
| Wrong decimal placement in product | Count total decimal places in both factors |
| Dividing by a decimal without converting | Convert divisor to whole number first |
| Forgetting to simplify final answer | Always reduce fractions to lowest terms |
8. CBSE exam focus
| Topic | Marks | Question style |
|---|---|---|
| Fraction multiplication/division | 2-3 marks | Direct and simplify |
| Decimal multiplication/division | 2-3 marks | Direct calculation |
| Word problems on fractions | 3 marks | Real-life applications |
| Word problems on decimals | 3 marks | Money, distance, capacity |
| Mixed operations | 4 marks | Combined fraction and decimal |
9. Self-test
- Multiply: (4/9) x (15/16).
- Divide: (9/11) / (18/22).
- Find: 0.056 x 1000.
- Evaluate: 7.2 / 0.09.
- A rope is 12.5 m long. It is cut into 5 equal pieces. How long is each piece?
- Ravi ate 2/5 of a pizza and Sita ate 1/3 of the same pizza. Who ate more and by how much?
10. Answer key
- (4 x 15) / (9 x 16) = 60/144 = 5/12.
- (9/11) x (22/18) = 198/198 = 1.
- 0.056 x 1000 = 56 (decimal shifts 3 places right).
- 7.2 / 0.09 = (7.2 x 100) / (0.09 x 100) = 720 / 9 = 80.
- Each piece = 12.5 / 5 = 2.5 m.
- Ravi's share = 2/5 = 6/15. Sita's share = 1/3 = 5/15. Ravi ate more by 1/15.
11. Quick revision
- Multiply fractions: numerator x numerator, denominator x denominator.
- Divide fractions: multiply by reciprocal.
- Multiply decimals: multiply as whole numbers, place decimal at sum of places.
- Divide decimals: convert divisor to whole number, adjust dividend accordingly.
- Simplify answers to lowest terms.
