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First you need to break the numbers into their prime factors. In this case we get:

63 = 3x3x7

21 = 3x7

The next step is to identify any common prime factors. In this case both have a 3 and a 7 as prime factors. Multiply these together and you get 3x7 = 21. This is the HCF. To find the LCM you just multiply the numbers together and divide by the HCF. 63x21/21 = 63

Thus 63 is the LCM.

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โˆ™ 2012-02-25 21:00:01
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Q: What is the HCF and LCM of 63 and 21?
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