How to Find the Greatest Common Factor for 12 and 21

You can find the greatest common factor (GCF) of 12 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 12 • The factors of 12 are the numbers that can evenly divide 12. In this case, they are 1, 2, 3, 4, 6, and 12. 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 12 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 12 and 21 is 3. So, the GCF of 12 and 21 is 3. Note: In this case, the greatest common factor is 3, which is the largest number that can evenly divide both 12 and 21.