Solution: The LCM of 90 and 81 is 810
Methods
How to find the LCM of 90 and 81 using Prime Factorization
One way to find the LCM of 90 and 81 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 90?
What are the Factors of 81?
Here is the prime factorization of 90:
2
1
×
3
2
×
5
1
2^1 × 3^2 × 5^1
2 1 × 3 2 × 5 1
And this is the prime factorization of 81:
3
4
3^4
3 4
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
2
1
×
3
4
×
5
1
=
810
2^1 × 3^4 × 5^1 = 810
2 1 × 3 4 × 5 1 = 810
Through this we see that the LCM of 90 and 81 is 810.
How to Find the LCM of 90 and 81 by Listing Common Multiples
The first step to this method of finding the Least Common Multiple of 90 and 81 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, 90 and 81:
What are the Multiples of 90?
What are the Multiples of 81?
Let’s take a look at the first 10 multiples for each of these numbers, 90 and 81:
First 10 Multiples of 90: 90, 180, 270, 360, 450, 540, 630, 720, 810, 900
First 10 Multiples of 81: 81, 162, 243, 324, 405, 486, 567, 648, 729, 810
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 90 and 81 are 810, 1620, 2430. Because 810 is the smallest, it is the least common multiple.
The LCM of 90 and 81 is 810.
Find the LCM of Other Number Pairs
Want more practice? Try some of these other LCM problems:
What is the LCM of 109 and 65?
What is the LCM of 145 and 124?
What is the LCM of 37 and 144?
What is the LCM of 55 and 78?
What is the LCM of 76 and 63?