Solution: The GCF of 12 and 123 is 3
Methods
How to find the GCF of 12 and 123 using Prime Factorization
One way to find the GCF of 12 and 123 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 12?
What are the Factors of 123?
Here is the prime factorization of 12:
2
2
×
3
1
2^2 × 3^1
2 2 × 3 1
And this is the prime factorization of 123:
3
1
×
4
1
1
3^1 × 41^1
3 1 × 4 1 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 12 and 123 by multiplying all the matching prime factors to get a GCF of 12 and 123 as 9:
Thus, the GCF of 12 and 123 is: 9
How to Find the GCF of 12 and 123 by Listing All Common Factors
The first step to this method of finding the Greatest Common Factor of 12 and 123 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, 12 and 123:
Factors of 12: 1, 2, 3, 4, 6, 12
Factors of 123: 1, 3, 41, 123
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 12 and 123 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 46 and 59?
What is the GCF of 117 and 136?
What is the GCF of 71 and 36?
What is the GCF of 24 and 146?
What is the GCF of 83 and 30?