Sometimes you are given numbers expressed as a product of prime factors. For example, 8 = 2 3 and 90 = 2 × 3 2 × 5. If you want to find the LCM and HCF in an exam, we can use prime factor form ...

To find the HCF, find any prime factors that are in common between the products. Each product contains two 2s and one 3, so use these for the HCF. HCF = \(2 \times 2 \times 3 = 12\) ...