New News Maths #6

Lowest Common Multiple

Lowest / Least Common Multiple (LCM) = the smallest number that is a multiple of all the numbers in question

Example: Find the LCM of 6 & 10 (write out some of the multiples separately for 6 & 10)

6 10

12 20

18 30

24 40

30 50

36 60

The LCM of 6 & 10 is 30

Example: Find the LCM of 28 & 42 (tip: use their prime factors)

42 = 2 * 3 * 7

28 = 2 * 2 * 7

If a number occurs in both lists, ‘only count them once’. Then multiply together the prime factors of both.

2 * 2 * 3 * 7 = 84