How do I solve HCF and LCM problems?

Find the prime factorisation of each number. Break each number down into a product of prime factors. For HCF: take the common prime factors with the lowest powers. Multiply them together.

What are common mistakes in HCF and LCM?

Confusing HCF and LCM — HCF is always smaller than or equal to both numbers. Missing a prime factor during factorisation.

Which class covers HCF and LCM?

HCF and LCM is typically taught in Class 5, 6, 7. SparkEd has free practice for all these grades.

Where can I practise HCF and LCM for free?

SparkEd offers free chapter-wise practice for HCF and LCM aligned to CBSE, ICSE, and IB curricula. Visit sparkedmaths.com to start.

How to Solve HCF and LCM — Step by Step Guide

Find the Highest Common Factor and Lowest Common Multiple. This guide covers Class 5 to 7.

Step-by-Step Method

1
Find the prime factorisation of each number. Break each number down into a product of prime factors.
2
For HCF: take the common prime factors with the lowest powers. Multiply them together.
3
For LCM: take all prime factors with the highest powers. Multiply them together.
4
Quick check: HCF × LCM = Product of the two numbers. Use this to verify your answer.

Worked Example

Problem: Find HCF and LCM of 12 and 18.

Solution: 12 = 2² × 3, 18 = 2 × 3². HCF = 2¹ × 3¹ = 6. LCM = 2² × 3² = 36. Check: 6 × 36 = 216 = 12 × 18.

Common Mistakes to Avoid

✗
Confusing HCF and LCM — HCF is always smaller than or equal to both numbers.
✗
Missing a prime factor during factorisation.
✗
Taking the highest power for HCF instead of the lowest.
✗
Not verifying using the relationship HCF × LCM = product of the numbers.

Practice HCF and LCM on SparkEd

Get free chapter-wise practice questions aligned to your board:

CBSE Class 6 Playing with Numbers ICSE Class 6 HCF and LCM

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Frequently Asked Questions

How do I solve HCF and LCM problems?: Find the prime factorisation of each number. Break each number down into a product of prime factors. For HCF: take the common prime factors with the lowest powers. Multiply them together.
What are common mistakes in HCF and LCM?: Confusing HCF and LCM — HCF is always smaller than or equal to both numbers. Missing a prime factor during factorisation.
Which class covers HCF and LCM?: HCF and LCM is typically taught in Class 5, 6, 7. SparkEd has free practice for all these grades.
Where can I practise HCF and LCM for free?: SparkEd offers free chapter-wise practice for HCF and LCM aligned to CBSE, ICSE, and IB curricula. Visit sparkedmaths.com to start.

SparkEd Maths — sparked.coms@gmail.com — www.sparkedmaths.com