To find the greatest Common factor of two numbers you must first find all of the factors of each given number. For example:
Find the Greatest Common Factor of 8 and 24.
1. Find all of the factors of 8
So, the factors of 8 are: 1,2,4,8 (the numbers that when multiplied together give you a product which equals the number you are working with)
2. Find the factors of 24.
So, the factors of 24 are: 1,2,3,4,6,8,12,24
The common factors of 8 and 24 are 1,2,4,8
The Greatest Common Factor (GCF) of 8 and 24 is 8
You can also find the GCF of two or more numbers using a factor tree.
Example: Find the GCF of 8 and 24 using a factor tree: