How to find the LCM- Least Common Multiple

The least common multiple, or LCM, of a group of numbers is the smallest (least) number that is a multiple of each of the numbers of that given set.

1. Find the LCM (least common multiple) of 8 and 12.
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B.
C.
D.

Question 1 of 2

2. Find the LCM (least common multiple) of 8 and 10.
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B.
C.
D.

Question 2 of 2


 

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Finding the LCM goes as follows:

First, list all multiples of each number in the set of numbers that are given.
Then, list all the multiples that they have in common.
Then, pick the least of all multiples that are they have in common.

For example, find the LCM (least common multiple) of 12 & 16.

Here’s the solution:

First, list all multiples of 12 & 16:

The multiples of 12 are: 12, 24, 36, 48, 60, 72, 84, 96, . . .
The multiples of 16 are: 16, 32, 48, 64, 80, 96, 112, . . .

Now, pick all common multiples.

The common multiples are 48, 96, . . .
So the LCM of 12 and 16 is the least of these common multiples.
The LCM of 12 and 16, or LCM (12,16), is 48.

One more example: Find the LCM (least common multiple) of 6 & 9:

The multiples of 6 are: 6, 12, 18, 24, 30, 36, 42, 48, 54,
The multiples of 9 are: 9, 18, 27, 36, 45, 54, 63, 72,…

The common multiples are 18, 54, …
As before, the LCM is the least (or smallest) of these common multiples.
So we write: LCM(6,9) = 18

Last Updated on August 18, 2020.

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