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 ...

1 is a common factor of all whole numbers. To find common factors: List the factors of each number. Compare the factors to find numbers that are the same (or common) in each list.