Solution: The LCM of 91 and 31 is 2821
Methods
How to find the LCM of 91 and 31 using Prime Factorization
One way to find the LCM of 91 and 31 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 91?
What are the Factors of 31?
Here is the prime factorization of 91:
7
1
×
1
3
1
7^1 × 13^1
7 1 × 1 3 1
And this is the prime factorization of 31:
3
1
1
31^1
3 1 1
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: 7, 13, 31
7
1
×
1
3
1
×
3
1
1
=
2821
7^1 × 13^1 × 31^1 = 2821
7 1 × 1 3 1 × 3 1 1 = 2821
Through this we see that the LCM of 91 and 31 is 2821.
How to Find the LCM of 91 and 31 by Listing Common Multiples
The first step to this method of finding the Least Common Multiple of 91 and 31 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, 91 and 31:
What are the Multiples of 91?
What are the Multiples of 31?
Let’s take a look at the first 10 multiples for each of these numbers, 91 and 31:
First 10 Multiples of 91: 91, 182, 273, 364, 455, 546, 637, 728, 819, 910
First 10 Multiples of 31: 31, 62, 93, 124, 155, 186, 217, 248, 279, 310
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 91 and 31 are 2821, 5642, 8463. Because 2821 is the smallest, it is the least common multiple.
The LCM of 91 and 31 is 2821.
Find the LCM of Other Number Pairs
Want more practice? Try some of these other LCM problems:
What is the LCM of 139 and 78?
What is the LCM of 35 and 8?
What is the LCM of 114 and 144?
What is the LCM of 34 and 71?
What is the LCM of 48 and 33?