Q:

What is the GCF of 21 and 141?

Accepted Solution

A:
Solution: The GCF of 21 and 141 is 3 Methods How to find the GCF of 21 and 141 using Prime Factorization One way to find the GCF of 21 and 141 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 21? What are the Factors of 141? Here is the prime factorization of 21: 3 1 × 7 1 3^1 × 7^1 3 1 × 7 1 And this is the prime factorization of 141: 3 1 × 4 7 1 3^1 × 47^1 3 1 × 4 7 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 21 and 141 by multiplying all the matching prime factors to get a GCF of 21 and 141 as 9: Thus, the GCF of 21 and 141 is: 9 How to Find the GCF of 21 and 141 by Listing All Common Factors The first step to this method of finding the Greatest Common Factor of 21 and 141 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, 21 and 141: Factors of 21: 1, 3, 7, 21 Factors of 141: 1, 3, 47, 141 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 21 and 141 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 37 and 19? What is the GCF of 108 and 32? What is the GCF of 2 and 109? What is the GCF of 9 and 138? What is the GCF of 66 and 133?