Intermediate Test Prep Math 8 (Grade 5) Greatest Common Factor

Greatest Common Factor
Lesson
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Merry Go Round

The greatest common factor (GCF)of two (or more) numbers is the largest number that is a factor of both numbers.

Review: A factor is a number that will go into another number evenly.

We can find the GCF by using factor trees and looking at the prime numbers they have in common. We then multiply those numbers together to find the GCF.

Take a look at this example:

What is the GCF of 48 and 24?

Let's see what the two numbers have in common...

Prime Factors

48: 2 · 2 · 2 · 2 · 3

24: 2 · 2 · 2 · 3

SO... When we multiply 2 · 2 · 2 · 3
we find our GCF to be 24.

Let's Practice!

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