Solution: The GCF of 100 and 81 is 1
Methods
How to find the GCF of 100 and 81 using Prime Factorization
One way to find the GCF of 100 and 81 is to compare 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 100?
What are the Factors of 81?
Here is the prime factorization of 100:
2
2
×
5
2
2^2 × 5^2
2 2 × 5 2
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 can see that there are no matching prime factors. When this is the case, it means that there are no common factors between these two numbers. As a result, the GCF of 100 and 81 is 1.
Thus, the GCF of 100 and 81 is: 1
How to Find the GCF of 100 and 81 by Listing All Common Factors
The first step to this method of finding the Greatest Common Factor of 100 and 81 is to find and list all the factors of each number. Again, you can see how this is done by looking at the “Factors of” articles that are linked to above.
Let’s take a look at the factors for each of these numbers, 100 and 81:
Factors of 100: 1, 2, 4, 5, 10, 20, 25, 50, 100
Factors of 81: 1, 3, 9, 27, 81
When you compare the two lists of factors, you can see that the only common factor is 1. So, in this case, the GCF of 100 and 81 is 1.
Find the GCF of Other Number Pairs
Want more practice? Try some of these other GCF problems:
What is the GCF of 40 and 58?
What is the GCF of 116 and 63?
What is the GCF of 50 and 131?
What is the GCF of 93 and 1?
What is the GCF of 81 and 102?