Solution: The GCF of 33 and 55 is 11MethodsHow to find the GCF of 33 and 55 using Prime FactorizationOne way to find the GCF of 33 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 33?What are the Factors of 55?Here is the prime factorization of 33:31×1113^1 × 11^131×111And this is the prime factorization of 55:51×1115^1 × 11^151×111When 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 33 and 55 by multiplying all the matching prime factors to get a GCF of 33 and 55 as 121:Thus, the GCF of 33 and 55 is: 121How to Find the GCF of 33 and 55 by Listing All Common FactorsThe first step to this method of finding the Greatest Common Factor of 33 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, 33 and 55:Factors of 33: 1, 3, 11, 33Factors of 55: 1, 5, 11, 55When 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 33 and 55 would be 11.Find the GCF of Other Number PairsWant more practice? Try some of these other GCF problems:What is the GCF of 34 and 128?What is the GCF of 84 and 14?What is the GCF of 113 and 71?What is the GCF of 57 and 63?What is the GCF of 58 and 90?