1. EXAMPLE 1 Finding the Greatest Common Factor Find the greatest common factor of 56 and 84. SOLUTION STEP 1 Write the prime factorization of each number. 56 = 2 2 2 7 84 = 2 2 3 7

2. EXAMPLE 1 Finding the Greatest Common Factor STEP 2 Find the common prime factors. They are 2, 2, and 7. The GCF of 56 and 84 is the product of these factors. ANSWER The GCF of 56 and 84 is 2 2 7, or 28.

3. GUIDED PRACTICE for Example 1 Find the greatest common factor of the numbers. 32 = 2 2 2 4 12 = 2 2 3 1. ANSWER The GCF of 12 and 32 is 2 2, or 4. 60 = 2 2 3 5 42 2. = 2 3 7 ANSWER The GCF of 42 and 60 is 2 3 or 6.

4. GUIDED PRACTICE for Example 1 Find the greatest common factor of the numbers. 90 = 2 3 3 5 36 3. = 2 3 3 3 ANSWER The GCF of 36 and 90 is 2 3 3 or 18. 96 4. = 2 2 2 3 4 120 = 2 2 2 3 5 ANSWER The GCF of 96 and 120 is 2 2 2 3 or 24.