Solution: The LCM of 28 and 108 is 756
Methods
How to find the LCM of 28 and 108 using Prime Factorization
One way to find the LCM of 28 and 108 is to start by comparing the prime factorization of each number. To find the prime factorization, you can follow the instructions for each number here:
What are the Factors of 28?
What are the Factors of 108?
Here is the prime factorization of 28:
2
2
×
7
1
2^2 × 7^1
2 2 × 7 1
And this is the prime factorization of 108:
2
2
×
3
3
2^2 × 3^3
2 2 × 3 3
When you compare the prime factorization of these two numbers, you want to look for the highest power that each prime factor is raised to. In this case, there are these prime factors to consider: 2, 7, 3
2
2
×
3
3
×
7
1
=
756
2^2 × 3^3 × 7^1 = 756
2 2 × 3 3 × 7 1 = 756
Through this we see that the LCM of 28 and 108 is 756.
How to Find the LCM of 28 and 108 by Listing Common Multiples
The first step to this method of finding the Least Common Multiple of 28 and 108 is to begin to list a few multiples for each number. If you need a refresher on how to find the multiples of these numbers, you can see the walkthroughs in the links below for each number.
Let’s take a look at the multiples for each of these numbers, 28 and 108:
What are the Multiples of 28?
What are the Multiples of 108?
Let’s take a look at the first 10 multiples for each of these numbers, 28 and 108:
First 10 Multiples of 28: 28, 56, 84, 112, 140, 168, 196, 224, 252, 280
First 10 Multiples of 108: 108, 216, 324, 432, 540, 648, 756, 864, 972, 1080
You can continue to list out the multiples of these numbers as long as needed to find a match. Once you do find a match, or several matches, the smallest of these matches would be the Least Common Multiple. For instance, the first matching multiple(s) of 28 and 108 are 756, 1512, 2268. Because 756 is the smallest, it is the least common multiple.
The LCM of 28 and 108 is 756.
Find the LCM of Other Number Pairs
Want more practice? Try some of these other LCM problems:
What is the LCM of 45 and 21?
What is the LCM of 34 and 67?
What is the LCM of 131 and 26?
What is the LCM of 90 and 82?
What is the LCM of 125 and 124?