Solution: The GCF of 126 and 15 is 3
Methods
How to find the GCF of 126 and 15 using Prime Factorization
One way to find the GCF of 126 and 15 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 126?
What are the Factors of 15?
Here is the prime factorization of 126:
2
1
×
3
2
×
7
1
2^1 × 3^2 × 7^1
2 1 × 3 2 × 7 1
And this is the prime factorization of 15:
3
1
×
5
1
3^1 × 5^1
3 1 × 5 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 126 and 15 by multiplying all the matching prime factors to get a GCF of 126 and 15 as 9:
Thus, the GCF of 126 and 15 is: 9
How to Find the GCF of 126 and 15 by Listing All Common Factors
The first step to this method of finding the Greatest Common Factor of 126 and 15 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, 126 and 15:
Factors of 126: 1, 2, 3, 6, 7, 9, 14, 18, 21, 42, 63, 126
Factors of 15: 1, 3, 5, 15
When you compare the two lists of factors, you can see that the common factor(s) are 1, 3. Since 3 is the largest of these common factors, the GCF of 126 and 15 would be 3.
Find the GCF of Other Number Pairs
Want more practice? Try some of these other GCF problems:
What is the GCF of 118 and 132?
What is the GCF of 76 and 34?
What is the GCF of 15 and 106?
What is the GCF of 100 and 134?
What is the GCF of 84 and 38?