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

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

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!!

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=

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

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.

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

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

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