Solution: The LCM of 18 and 140 is 1260
Methods
How to find the LCM of 18 and 140 using Prime Factorization
One way to find the LCM of 18 and 140 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 18?
What are the Factors of 140?
Here is the prime factorization of 18:
2
1
×
3
2
2^1 × 3^2
2 1 × 3 2
And this is the prime factorization of 140:
2
2
×
5
1
×
7
1
2^2 × 5^1 × 7^1
2 2 × 5 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: 2, 3, 5, 7
2
2
×
3
2
×
5
1
×
7
1
=
1260
2^2 × 3^2 × 5^1 × 7^1 = 1260
2 2 × 3 2 × 5 1 × 7 1 = 1260
Through this we see that the LCM of 18 and 140 is 1260.
How to Find the LCM of 18 and 140 by Listing Common Multiples
The first step to this method of finding the Least Common Multiple of 18 and 140 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, 18 and 140:
What are the Multiples of 18?
What are the Multiples of 140?
Let’s take a look at the first 10 multiples for each of these numbers, 18 and 140:
First 10 Multiples of 18: 18, 36, 54, 72, 90, 108, 126, 144, 162, 180
First 10 Multiples of 140: 140, 280, 420, 560, 700, 840, 980, 1120, 1260, 1400
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 18 and 140 are 1260, 2520, 3780. Because 1260 is the smallest, it is the least common multiple.
The LCM of 18 and 140 is 1260.
Find the LCM of Other Number Pairs
Want more practice? Try some of these other LCM problems:
What is the LCM of 132 and 8?
What is the LCM of 126 and 115?
What is the LCM of 142 and 17?
What is the LCM of 147 and 137?
What is the LCM of 81 and 12?