Solution: The GCF of 121 and 55 is 11
Methods
How to find the GCF of 121 and 55 using Prime Factorization
One way to find the GCF of 121 and 55 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 121?
What are the Factors of 55?
Here is the prime factorization of 121:
1
1
2
11^2
1 1 2
And this is the prime factorization of 55:
5
1
×
1
1
1
5^1 × 11^1
5 1 × 1 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 121 and 55 by multiplying all the matching prime factors to get a GCF of 121 and 55 as 121:
Thus, the GCF of 121 and 55 is: 121
How to Find the GCF of 121 and 55 by Listing All Common Factors
The first step to this method of finding the Greatest Common Factor of 121 and 55 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, 121 and 55:
Factors of 121: 1, 11, 121
Factors of 55: 1, 5, 11, 55
When you compare the two lists of factors, you can see that the common factor(s) are 1, 11. Since 11 is the largest of these common factors, the GCF of 121 and 55 would be 11.
Find the GCF of Other Number Pairs
Want more practice? Try some of these other GCF problems:
What is the GCF of 48 and 38?
What is the GCF of 133 and 81?
What is the GCF of 12 and 59?
What is the GCF of 119 and 104?
What is the GCF of 127 and 24?