How to Find the Greatest Common Factor for 9 and 21

You can find the greatest common factor (GCF) of 9 and 21 by listing the common factors for each number and then identifying the greatest factor in each list. Here's the step-by-step process: Step 1: List the Factors of 9 • The factors of 9 are the numbers that can evenly divide 9. In this case, they are 1, 3, and 9. Step 2: List the Factors of 21 • The factors of 21 are the numbers that can evenly divide 21. In this case, they are 1, 3, 7, and 21. Step 3: Identify the Common Factors • Compare the lists of factors for 9 and 21 to find the common factors. The common factors are the numbers that appear in both lists. Common Factors: 1, 3 Step 4: Determine the Greatest Common Factor • Finally, determine which common factor is the greatest. In this case, the greatest common factor (GCF) of 9 and 21 is 3. So, the GCF of 9 and 21 is 3. Note: You can also use prime factorization to find the GCF. It involves breaking down each number into its prime factors and then finding the common prime factors.