Solution: The LCM of 40 and 72 is 360
Methods
How to find the LCM of 40 and 72 using Prime Factorization
One way to find the LCM of 40 and 72 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 40?
What are the Factors of 72?
Here is the prime factorization of 40:
2
3
×
5
1
2^3 × 5^1
2 3 × 5 1
And this is the prime factorization of 72:
2
3
×
3
2
2^3 × 3^2
2 3 × 3 2
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, 5, 3
2
3
×
3
2
×
5
1
=
360
2^3 × 3^2 × 5^1 = 360
2 3 × 3 2 × 5 1 = 360
Through this we see that the LCM of 40 and 72 is 360.
How to Find the LCM of 40 and 72 by Listing Common Multiples
The first step to this method of finding the Least Common Multiple of 40 and 72 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, 40 and 72:
What are the Multiples of 40?
What are the Multiples of 72?
Let’s take a look at the first 10 multiples for each of these numbers, 40 and 72:
First 10 Multiples of 40: 40, 80, 120, 160, 200, 240, 280, 320, 360, 400
First 10 Multiples of 72: 72, 144, 216, 288, 360, 432, 504, 576, 648, 720
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 40 and 72 are 360, 720, 1080. Because 360 is the smallest, it is the least common multiple.
The LCM of 40 and 72 is 360.
Find the LCM of Other Number Pairs
Want more practice? Try some of these other LCM problems:
What is the LCM of 86 and 106?
What is the LCM of 67 and 90?
What is the LCM of 59 and 31?
What is the LCM of 32 and 89?
What is the LCM of 95 and 119?