LCM and HCF practice for 11+
26 October 2026
Why LCM and HCF matter for 11+
Understanding Highest Common Factor (HCF) and Least Common Multiple (LCM) is key for 11+ Maths. These topics appear in both CEM and GL style exams. Practising them helps children spot patterns, work with factors and multiples, and solve more complex problems with fractions and ratios.
Practice questions for LCM and HCF
Try these questions with your child:
1. Find the HCF of 16 and 24.
2. What is the LCM of 6 and 8?
3. List all the factors of 30.
4. What is the smallest number that is a multiple of both 9 and 12?
5. Find the HCF and LCM of 15 and 25.
Worked example: Finding HCF and LCM
Let's work through an example with 12 and 18.
Step 1: List the factors of both numbers
Factors of 12: 1, 2, 3, 4, 6, 12
Factors of 18: 1, 2, 3, 6, 9, 18
Step 2: Identify the common factors
Common factors: 1, 2, 3, 6
Step 3: Find the Highest Common Factor (HCF)
The largest number in both lists is 6. So, the HCF of 12 and 18 is 6.
Step 4: List the first few multiples of each number
Multiples of 12: 12, 24, 36, 48, 60, 72
Multiples of 18: 18, 36, 54, 72, 90
Step 5: Find the Least Common Multiple (LCM)
The smallest number in both lists is 36. So, the LCM of 12 and 18 is 36.
Key insight: Build confidence step by step
Children learn best by understanding the process and practising with different examples. Encourage them to list factors and multiples clearly, and to check their answers carefully.
