Solution: The GCF of 143 and 138 is 1MethodsHow to find the GCF of 143 and 138 using Prime FactorizationOne way to find the GCF of 143 and 138 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 143?What are the Factors of 138?Here is the prime factorization of 143:111×13111^1 × 13^1111×131And this is the prime factorization of 138:21×31×2312^1 × 3^1 × 23^121×31×231When you compare the prime factorization of these two numbers, you can see that there are no matching prime factors. When this is the case, it means that there are no common factors between these two numbers. As a result, the GCF of 143 and 138 is 1.Thus, the GCF of 143 and 138 is: 1How to Find the GCF of 143 and 138 by Listing All Common FactorsThe first step to this method of finding the Greatest Common Factor of 143 and 138 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, 143 and 138:Factors of 143: 1, 11, 13, 143Factors of 138: 1, 2, 3, 6, 23, 46, 69, 138When you compare the two lists of factors, you can see that the only common factor is 1. So, in this case, the GCF of 143 and 138 is 1.Find the GCF of Other Number PairsWant more practice? Try some of these other GCF problems:What is the GCF of 117 and 122?What is the GCF of 139 and 42?What is the GCF of 60 and 106?What is the GCF of 118 and 142?What is the GCF of 131 and 65?