Greatest Common Factor (GCF)

What prime factorization is. For example the prime factorization of 24 = 2•2•2•3 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 number24 = 2•2•2•332 = 2•2•2•2•2

Step 2: Circle common prime factors Step 3: Multiply common factors GCF = 2•2•2 = 8

Find the GCF of 72 and 48 Step 1: Find the prime factorization of

each number72 = 2•2•2•3•348 = 2•2•2•2•3

Step 2: Circle common prime factors Step 3: Multiply common factors GCF = 2•2•2•3 = 24

Find the GCF of the following sets of numbers

A) 36, 48 B) 45, 24 C) 15, 32