Solution: The LCM of 57 and 42 is 798
Methods
How to find the LCM of 57 and 42 using Prime Factorization
One way to find the LCM of 57 and 42 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 57?
What are the Factors of 42?
Here is the prime factorization of 57:
3
1
×
1
9
1
3^1 × 19^1
3 1 × 1 9 1
And this is the prime factorization of 42:
2
1
×
3
1
×
7
1
2^1 × 3^1 × 7^1
2 1 × 3 1 × 7 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: 3, 19, 2, 7
2
1
×
3
1
×
7
1
×
1
9
1
=
798
2^1 × 3^1 × 7^1 × 19^1 = 798
2 1 × 3 1 × 7 1 × 1 9 1 = 798
Through this we see that the LCM of 57 and 42 is 798.
How to Find the LCM of 57 and 42 by Listing Common Multiples
The first step to this method of finding the Least Common Multiple of 57 and 42 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, 57 and 42:
What are the Multiples of 57?
What are the Multiples of 42?
Let’s take a look at the first 10 multiples for each of these numbers, 57 and 42:
First 10 Multiples of 57: 57, 114, 171, 228, 285, 342, 399, 456, 513, 570
First 10 Multiples of 42: 42, 84, 126, 168, 210, 252, 294, 336, 378, 420
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 57 and 42 are 798, 1596, 2394. Because 798 is the smallest, it is the least common multiple.
The LCM of 57 and 42 is 798.
Find the LCM of Other Number Pairs
Want more practice? Try some of these other LCM problems:
What is the LCM of 26 and 23?
What is the LCM of 56 and 148?
What is the LCM of 16 and 31?
What is the LCM of 27 and 7?
What is the LCM of 47 and 4?