How do you find the Greatest Common Factor?

The GCF, is the greatest factor that divides 2 numbers. To find the GCF of 2 numbers: List the prime factors of each number. Multiply those factors both numbers have in common

You first list out all the factors.

For example, 25 and 30.

25: 1, 5, 25

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

Second, you look at all the common factors.

The common factors are: 1, and 5.

Finally, you take the greatest common factor.

That would be 5. So, the GCF of 25 and 30 is 5.