greatest common factor

Greatest Common Factor (GCF) Review

GCF Review

Step 1: List the prime factors of each number using factor trees

Step 2: Identify the prime factors that both numbers have in common.

Step 3: Multiply the common factors together

Step 4: The product is the GCF. If there are no common prime factors the GCF is 1

List the factors

List the factors for each number, starting with 1 and the number itself. Then arrange the numbers in order from least to greatest.

Practice finding the GCF for the following.

Multiple Choice

Find the GCF for 12 & 22

• 12

• 2

• 22

• 11

Multiple Choice

Find the GCF of 45 & 27

• 9

• 12

• 45

• 1

Multiple Choice

Find the GCF of 36 & 42

• 9

• 8

• 6

• 12