Finding the Greatest Common Factor

Here is a little flash file that I created this morning to hopefully help you understand how to find the greatest common factor between two numbers. I hope to add audio to this later but don't have the time at the moment.

To find the greatest common factor between 18 and 24 first you need to find the prime factorization of each. To do this divide 18 by 2 and you get 9. Nine is not a prime, it can be divided by 3. So the prime factorization of 18 is 2x3x3. Next do the same with 24. Twenty-four divided by 4 is 6. Neither 4 or 6 are prime so they need to be broken down farther. Four is divisible by 2 and 6 is divisible by 2 and 3. Making the prime factorization of 24 = 2x2x2x3.

Next find the common numbers that are in each prime factorization of each number. Both 18 and 24 contain a 2 and a 3. Multiply these together to get 6. Thus 6 is the greatest common factor of 18 and 24.

To download this file simply right click the link below and select Save As... or Save Target As...