What is LCM?

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LCM is an acronym for Least Common Multiple or Lowest Common Multiple. It is an integral aspect in mathematics distinguished as two or more multiples of a certain number. For instance, if you want to find the LCM of 3 and 5, you first need to least all the multiples of number “3”. That is 0, 3, 6, 12, 15, 18, 24, and so on and so forth. Next, you need to least all the multiples of “5” which is 0, 5, 10, 15, 20, 25, and 30. The LCM is the smallest number that is common for both “3” and “5” which is 15.

There are many ways to get the LCM. In larger numbers, a method known as Prime Factorization is used. Let us say you are looking for the LCM of two-digit numbers like 20 and 42. The first thing you need to do is factor both number down to their prime numbers. Next, you multiply the prime numbers and get the product. The factoring is done like this: 20 = 2 x2 x5 and 42 = 2 x 3 x 7. Take note of how many times each multiple is mentioned. Number “2” is mentioned twice so it has to be multiplied by 2. Hence, the answer is 4. On the other hand, 3, 5, 7, are only mentioned once, so there is no need to multiply them. When 4, 3, 5, and 7 is multiplies, the answer is 420 which is the LCM of 20 and 42.

Another way to find the LCM is using the Common Factors Grid (CFG). CFG is a longer method compared to prime factorization. In doing mathematics, many students would prefer either the latter or the listing of integers. Listing of integers, however, is only feasible in one-digit numbers.