1. HCF and LCM Primes Press Ctrl-A ©2009 G Dear – Not to be sold/Free to use Stage 4 Years 7 & 8 Web Resources

2. 2 HCF/LCM and Prime Factor (1/3)1218 3 4 3 22 2 9 33 2 x xx x xx Prime Factors 12 = 2 x 2 x 3 Prime Factors 18 = 2 x 3 x 3 Circle the common factors HCF = 2 x 3 = 6 1218 Find the HCF of 12 and 18. LCM = HCF x 2 x 3 Underline the remaining numbers = 6 x 2 x 3 = 36 End of Slide

3. 3 HCF/LCM and Prime Factor (2/3)2745 3 9 3 33 3 15 35 3 x xx x xx Prime Factors 27 = 3 x 3 x 3 Prime Factors 45 = 3 x 3 x 5 Circle the common factors HCF = 3 x 3 = 9 2745 Find the HCF of 27 and 45. LCM = HCF x 3 x 5 Underline the remaining numbers = 9 x 3 x 5 = 135 End of Slide

4. 4 HCF and LCM (3/3)Exercises Use Prime Factor Trees to find the HCF and LCM of: a) 24 and 36 b) 36 and 54 c) 24 and 56 d) 54 and 56 e) 60 and 36 f) 15 and 40 End of Slide