GCSE Maths (AQA)

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LCM & Prime Factorisations

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Number Structure and Calculation

LCM & Prime Factorisations

4:10 HCF & LCM
Spec N4
Previous Lowest Common Multiple Next Negative Indices
  • The lowest common multiple (LCM) can be found using prime factor trees and Venn diagrams
  • Prime factor trees are used to find all the prime factors of a number
  • Venn diagrams are used to sort data into groups or sets
  • In a Venn diagram, if a number is in both sets, it is written once in the intersection of the two sets
  • The LCM is the product of all the numbers in the Venn diagram
  • To find the LCM of more than two numbers, draw more intersecting circles representing the sets
  • Example: LCM of 12 and 18 is 36
  • Example: LCM of 18 and 42 is 126
  • Step 1: Find the prime factorization of each number using a factor tree
  • Step 2: Complete a Venn diagram of the prime factors of each number
  • Step 3: Find the LCM by multiplying all the numbers in the Venn diagram

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