![\"\"](\"http://www.mathskey.com/userfiles/image/steps_images/step1.JPG\")
Method 1:
\List the factors of each number.
\Factors of 27: 3, 9, 27
\Factors of 45: 3, 5, 9, 15,45
\Factors of 90: 2, 3, 5, 6, 9, 10, 15, 30, 45, 90
\Identify the greatest common factor.
\The greatest common factor of 27, 45 and 90 is 9.![\"\"](\"http://www.mathskey.com/userfiles/image/steps_images/step2.JPG\")
Method 2:
\Write the prime factorization of each number.
\27 = 3 × 3 × 3.
\45 = 3 × 3 × 5.
\90 = 2 × 3 × 3 × 5.
\The GCF is the product of the common prime factors in each number.
\GCF = 3 × 3 = 9
\The greatest common factor of 27, 45 and 90 is 9.![\"\"](\"http://www.mathskey.com/userfiles/image/steps_images/solution.JPG\")
The greatest common factor of 27, 45 and 90 is 9.