GCF

Finding the Greatest Common Factor of Two Numbers Cont.

Suppose we would like to find the greatest common factor of
18 and 30

First, we factor 18 into its prime factors.
18 = 2 x 3 x 3

Next we factor 30 into its prime factors.
30 = 2 x 3 x 5

What factors do 18 and 30 have in common?

    The factors 18 and 30 have in common are 2 and 3.
     18 = 2 x 3 x 3
     30 = 2 x 3 x 5

The Greatest Common Factor or GCF is 2 x 3 = 6 , for 18 and 30

What is the GCF for 70 and 42? When you are ready to answer click here.