 What prime factorization is.  For example the prime factorization of 24 = 2223  Today we will learn how to find the greatest common factor of two quantities.

 Greatest common factor or GCF is the largest factor that the two numbers have in common. For example, the greatest common factor of 12 and 18 is 6.  The way we find it is by using prime factorization and circling common prime factors.

 Find the GCF of 24 and 32  Step 1: Find the prime factorization of each number 24 = =  Step 2: Circle common prime factors  Step 3: Multiply common factors  GCF = 222 = 8

 Find the GCF of 72 and 48  Step 1: Find the prime factorization of each number 72 = =  Step 2: Circle common prime factors  Step 3: Multiply common factors  GCF = 2223 = 24

 Find the GCF of the following sets of numbers  A) 36, 48  B) 45, 24  C) 15, 32