Greatest Common Factor (GCF) (Jump to: Lecture | Video )

Greatest Common Factor (GCF)

The Greatest Common Factor (GCF) is the largest prime factor shared by two or more numbers.

What is the GCF of 18 and 36? Let's use factor trees to solve the problem:

Figure 1.

Both numbers share the factoring "2 x 3 x 3". Thus, the Greatest Common Factor is 18.


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