1. Prime Factorisation

2. Starter- Make a list of all the prime numbers between 1 and 50 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47 Remember- a prime has exactly two factors

3. Write 24 in prime factor form… 24 212 26 23 So 24 = 2 x 2 x 2 x 3

4. Write 30 in prime factor form… 30 215 35 So 30 = 2 x 3 x 5

5. Write these numbers in prime factor form…..  (a) 12  (b) 20  (c) 30  (d) 48  (e) 100  (f) 120

6. Highest Common Factor  Example- Find the HCF of 12 and 18 Write out all the factors of each number Write out all the factors of each number 12:- 1, 2, 3, 4, 6, 12 12:- 1, 2, 3, 4, 6, 12 18:- 1, 2, 3, 6, 18 18:- 1, 2, 3, 6, 18 The HCF is the biggest number that is in both lists The HCF is the biggest number that is in both lists HCF of 12 and 18 = 6 HCF of 12 and 18 = 6

7. Lowest Common Multiple  Example- Find the LCM of 6 and 8 Write out the first few multiples of each number Write out the first few multiples of each number 6:- 6, 12, 18, 24, 30, 36, 42, 48, 54, 60,.. 6:- 6, 12, 18, 24, 30, 36, 42, 48, 54, 60,.. 8:- 8, 16, 24, 32, 40, 48, 56, 64, …… 8:- 8, 16, 24, 32, 40, 48, 56, 64, …… The LCM is the lowest number in both lists The LCM is the lowest number in both lists So the LCM of 6 and 8 = 48 So the LCM of 6 and 8 = 48