![\"\"](\"http://www.mathskey.com/userfiles/image/steps_images/step1.JPG\")
Method 1:
\List the factors of each number.
\Factors of 20: 2, 4, 5, 10, 20
\Factors of 30: 3, 5, 6, 10, 30
\Identify the greatest common factor.
\The greatest common factor of 20 and 30 is 10.
\![\"\"](\"http://www.mathskey.com/userfiles/image/steps_images/step2.JPG\")
Method 2:
\Write the prime factorization of each number.
\20 = 2 × 2 × 5 .
\30 = 3 × 2 × 5 .
\The GCF is the product of the common prime factors in each number.
\GCF = 2 × 5 = 10.
\The greatest common factor of 20 and 30 is 10.
\![\"\"](\"http://www.mathskey.com/userfiles/image/steps_images/solution.JPG\")
The greatest common factor of 20 and 30 is 10.
\