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Here are some tips for Greatest Common Factor, which aligns with California state standards:

**Greatest Common Factor**

To review factoring, see here.

To find the greatest common factor, you need to figure out all of the factors and then simply pick the largest one.

**Example 1: Find the GCF of 16 and 24**

Factors of 16: 1,2,4,**8**,16

Factors of 24: 1,2,3,4,6,**8**,12,24

The greatest common factor is 8.

**Example 2: Find the GCF of 16 and 24**

Prime Factors of 16: **2*****2*****2***2

Prime Factors of 24: **2*****2*****2***3

The greatest common factor is 2*2*2=8

This technique is much faster than the technique used in example 1. If you want to excel, use this technique.

**Example 3: Find the GCF of 48 and 64**

The difference is 64 - 48 = 16. (16 is the third number as mentioned in the tip)

Does 16 go into 48? Yes, so the GCF is 16.

**Example 4: Find the GCF of 91 and 77**

91 - 77 = 14

Does 14 go into 77? no

What are the prime factors of 14? 2 and 7

Does 2 go into 77? no

Does 7 go into 77? yes

Therefore, the GCF of 91 and 77 is 7.

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