SOLUTION: Find the least number which is both a multiple of 20 and a multiple of 21.

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Question 323579: Find the least number which is both a multiple of 20 and a multiple of 21.
Answer by Edwin McCravy(20056)   (Show Source): You can put this solution on YOUR website!

Find the least number which is both a multiple of 20 and a multiple of 21

20 = 4x5 = 2x2x5
21 = 3x7

The prime factors of 20 are two 2's and one 5
Te prime factors of 21 are one 3 and one 7.

Since there are no common prime factors, the LCM (least common multiple)
is just their product 20x21 = 420.

Edwin
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