Class 8 Maths – Chapter 16: Playing with Numbers
Step 7: LCM & HCF using Prime Factorisation
LCM (Least Common Multiple) and HCF (Highest Common Factor) are very important exam topics.
🔹 Prime Factorisation Method
Break each number into a product of prime numbers.
📘 Example
Find the LCM and HCF of 36 and 48
Prime factorisation:
- 36 = 2 × 2 × 3 × 3 = 2² × 3²
- 48 = 2 × 2 × 2 × 2 × 3 = 2⁴ × 3
🔹 HCF
Take the lowest power of common prime factors:
HCF = 2² × 3 = 12
🔹 LCM
Take the highest power of all prime factors:
LCM = 2⁴ × 3² = 144
📝 Exam Writing Steps
- Write prime factorisation clearly
- Underline common factors
- Use lowest power for HCF
- Use highest power for LCM
🧠 Easy Memory Trick
HCF → Lowest powers 😌
LCM → Largest powers 😄
Conclusion:
HCF = 12
LCM = 144
📘 Class 8 Mathematics – Complete Library
CBSE | NCERT | State Syllabus
Chapter 1: Rational Numbers
Chapter 2: Linear Equations in One Variable
Chapter 3: Understanding Quadrilaterals
Chapter 4: Practical Geometry
Chapter 5: Data Handling
Chapter 6: Squares and Square Roots
Chapter 7: Cubes and Cube Roots
- NCERT Notes
- MCQs
- Worksheet
- Worksheet Answers
- Mind Map & Easy Tricks
- Important Exam Questions
- Very Important Questions
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