1. 06 GCF Greatest Common Factor GCF Greatest means _________ Biggest, Largest, Highest Common means ________ Share, have the same, be alike A Factor is _________ When one # goes into another # evenly … 10 ÷ 5 = 2 so 5 is a factor of 10

2. There’s 2 ways to Find GCF 1)Make a systematic list. Pattern 2)Use Prime Factors [we will learn this way later]

3. Making a List Let’s find all the factors of 12 ALWAYS start with 1 x ____ 1 x 12 2 x __use divisibility rules…does 2 work? 3 x __use divisibility rules…does 3 work? We are DONE cuz 3 & 4 are right next to each other!!

4. How do we know when we are DONE? 1 x 12 2 x 6 3 x 4 1x12= 2x6= 3x4= 4x3= 5x2.4=12 6x2= 7x1.7=12 8x1.5=12 9x1.3=12 10x1.2=12 11x1.1=12 x1=

5. Summarize Factors 12: 1, 2, 3, 4, 6, 12 1 x 12 2 x 6 3 x 4

6. Try another example Let’s find all the factors of 18 ALWAYS start with 1 x ____ 1 x 18 2 x __use divisibility rules…does 2 work? 3 x __use divisibility rules…does 3 work? 4 x __…does 4 work? 5 x __use divisibility rules…does 5 work? We are DONE cuz 3,4,5, 6 … 6 is already on the list so we are working back up.

7. Summarize Factors 18: 1, 2, 3, 6, 9, 18 1 x 18 2 x 9 3 x 6

8. All Common Factors 18: 1, 2, 3, 6, 9, 18 12: 1, 2, 3, 4, 6, 12 What one is the Greatest?

9. http://www.youtube.com/watch?v=i9M9KHfW9nE&feature=relatedhttp://www.youtube.com/watch?v=i9M9KHfW9nE&feature=related [1:34] http://www.youtube.com/watch?v=goIyymVmgCM&feature=relatedhttp://www.youtube.com/watch?v=goIyymVmgCM&feature=related [1:56] http://www.youtube.com/watch?v=9vScvHFvV14&feature=relatedhttp://www.youtube.com/watch?v=9vScvHFvV14&feature=related [2:51] http://www.khanacademy.org/video/greatest-common-divisor?playlist=Arithmetic