Solutions by everydaycalculation.com

The LCM of 21 and 20 is 420.

- Find the prime factorization of 21

21 = 3 × 7 - Find the prime factorization of 20

20 = 2 × 2 × 5 - Multiply each factor the greater number of times it occurs in steps i) or ii) above to find the LCM:

LCM = 2 × 2 × 3 × 5 × 7 - LCM =
**420**

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Find least common multiple (LCM) of: 42 & 40 63 & 60 105 & 100 147 & 140 42 & 20 21 & 40 63 & 20 21 & 60 105 & 20 21 & 100 147 & 20 21 & 140

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