How to find the LCM
The lowest common multiple is the smallest number that every number in the list divides into. One quick method uses the HCF: LCM(a, b) = a × b ÷ HCF(a, b). For 4 and 6: 24 ÷ 2 = 12. With more numbers, repeat: LCM(12, 10) = 120 ÷ 2 = 60, so LCM(4, 6, 10) = 60.
A classic exam question: buses leave every 12 minutes and trains every 20 minutes. When do they next leave together? LCM(12, 20) = 60 minutes. You also need the LCM to find the lowest common denominator when adding fractions.
Frequently asked questions
What is the LCM of 4 and 6?
12.
Is LCM the same as lowest common denominator?
The lowest common denominator is the LCM of the denominators.
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