Greatest Common Factor

Greatest Common Factor: For any two non-zero whole numbers a and b, the greatest common factor, usually written GCF(a,b). There are several methods to find the GCF of two numbers such as 1) List the Factors, 2) Prime Factorization, and 3) Linear ( Cuisenaire rods).

Listing Factor
To use this method you list the multiples that equal each number a and b. For this example it is 36 and 54

Linear ( Rods)

Prime Factorization

When dealing with the prime factorization of a number you start with the number and you break it down into all the multiples the number has using the prime numbers that are left and comparing and seeing what the other side has.

( for this example we are using 240 and 28 for example.) 

Since they only share 2x2 when u multiply those you get 4 as the GCF, so it will be written like GCF(240,28) is 4.

( Here is a Fun and interesting video to look for more help with Prime Factorization) 

http://www.math.com/school/subject1/lessons/S1U3L2GL.html 

(Above is a link to a great site to help you step by step to finding GCF!)