1. OMG! Its… GCF Greatest Common Factor
Prepare for Cornell notes

2. GFC…just break it down GFC is simply ….
the greatest number that is a factor of two or more numbers …. is called Greatest Common Factor.
Greatest number = the highest possible number
Factor = a number that makes up a product
Example: 3 x 2 = ,2 are the factors and 6 is the product
Factor….. Think of facts
Facts make up a story.
Facts are all the smaller details that
together make the whole story
so…..

3. Factors make the Product
Just as facts make the story
Factors should always be smaller than the numbers you are comparing…or at least same as one of the numbers.
Example:
Find the GCF of 6 and 12
6 is a factor of 12 ….2x6 =12
6 is a factor of 6 …..1x6= 6

4. Method to Finding GCF The are 2 basic methods to finding GCF
Depending on your style you may prefer one over the other. However, you will learn both and will be able to successfully use both as you will be asked on various tests to prove that you can solve using a particular method.
The methods are referred to as
1. Listing Method
2.Prime factorization aka “factor trees”
There is a brain pop that is helpful for prime factorization ….if you have time…<3 tiff

5. Listing Method Find the GCF of 12 and 20 1) List the factors of each.
2) Pick out the common factors
3) Select the Greatest.
Easy- Squeezie!!

6. What is a Prime Factor?!? Prime Factor …. Prime factorization….
Number that can not be factored any lower/smaller than 1, and itself …. Like 2, 3, 5, 7, Not 6… 2x3 or 8…2x4 is finding the factors of a number that are all prime.
Brain Pop for this!!! Prime Factorization

7. Prime Factorization aka “Factor Trees”
Easy to remember …THEY LOOK LIKE TREES!!
Christmas to be exact.

8. Prime factorization 84
/ \
42 x 2 (84 is 42 times 2)
21 x 2 (42 is 21 times 2)
/ \
7 x 3 (21 is 7 times 3)
(7 and 3 are both prime, so we stop!)
So the prime factors of 84 are 7 x 3 x 2 x 2.

Here's how you do it: Find 2 factors of your number. Then look at your 2 factors and determine if one or both of them is not prime. If it is not a prime factor it. Repeat this process until all your factors are prime.
Find the prime factors of the number 84: on you white board….hold it up when you done.
Here's an example: 


9. Using Prime Factorization to find GCF
1) Create a factor tree for both numbers.
2) Circle the Common Prime the end)
3) Multiply the common prime factors.
4) The product (answer) is your GCF!!
Find the GCF of 30 & / \ / \ /\ /\ x5x2= 30 /\ 2 2 2x3x2x2= 24 2x3=6 6 is the GCF!!!!