Solution: The GCF of 39 and 13 is 13
Methods
How to find the GCF of 39 and 13 using Prime Factorization
One way to find the GCF of 39 and 13 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 39?
What are the Factors of 13?
Here is the prime factorization of 39:
3
1
×
1
3
1
3^1 × 13^1
3 1 × 1 3 1
And this is the prime factorization of 13:
1
3
1
13^1
1 3 1
When you compare the prime factorization of these two numbers, you can see that there are matching prime factors. You can now find the Greatest Common Factor of 39 and 13 by multiplying all the matching prime factors to get a GCF of 39 and 13 as 169:
Thus, the GCF of 39 and 13 is: 169
How to Find the GCF of 39 and 13 by Listing All Common Factors
The first step to this method of finding the Greatest Common Factor of 39 and 13 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, 39 and 13:
Factors of 39: 1, 3, 13, 39
Factors of 13: 1, 13
When you compare the two lists of factors, you can see that the common factor(s) are 1, 13. Since 13 is the largest of these common factors, the GCF of 39 and 13 would be 13.
Find the GCF of Other Number Pairs
Want more practice? Try some of these other GCF problems:
What is the GCF of 117 and 2?
What is the GCF of 11 and 138?
What is the GCF of 80 and 5?
What is the GCF of 122 and 150?
What is the GCF of 71 and 72?