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A2. HCFs and LCMs
Least common multiple

Vocabulary Because 3 divides into 12 exactly, 3 is called a factor, or divisor, of 12. We also describe 12 as a multiple of 3. Other factors of twelve are 1, 2, 4, 6 and 12. The smalled common multiple of two given numbers is called their least common multiple . 12 is a multiple of 3. 12 is also a multiple of 2. Therefore 2 and 3 have a common multiple of 12. The other common multiples, besides 12, of 2 and 3 are: 6, 18, 24, 30 and so on. 6 is the smallest in this list and is therefore the least common multiple (LCM) of 2 and 3. The least common multiple of 8 and 6 is 24. The least common multiple of 12 and 10 is 60. One way to work out the LCM of two numbers is to write each one as a product of their prime factors, and then pick out all the highest power of every factor mentioned. 8=2 x 2 x 2=23 20=2 x 2 x 5=22 x 51 The highest powers of factors=23 x 51=40, so 40 is the LCM of 8 and 20. Find the LCM of two numbers yourself and check your answer. The correct answer is shown if you are wrong. Press the button to get started. The LCM=

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