What are two methods to find GCF?

Answer 1

1. Prime factorization

Example: 30 and 42

Factor them.

2 x 3 x 5 = 30

2 x 3 x 7 = 42

Select the common factors.

2 x 3 = 6, the GCF

2. List

Example: 30 and 42

The factors of 30 are:

1, 2, 3, 5, 6, 10, 15, 30

The factors of 42 are:

1, 2, 3, 6, 7, 14, 21, 42

The common factors are:

1, 2, 3, 6

The Greatest Common Factor:

GCF = 6