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Greatest common factor review

Review greatest common factors (GCF) and try some practice problems.

What is GCF?

GCF stands for greatest common factor. The greatest common factor of two numbers is the greatest number that is a factor of both of them.

Finding greatest common factor

One way to find the GCF of two (or more!) numbers is to list the factors of each number and find the greatest factor they have in common.
Want to learn more about greatest common factors? Check out this video.

Example: GCF of 12 and 18

Factors of 12: 1,2,3,4,6,12
Factors of 18: 1,2,3,6,9,18
1,2,3 and 6 are common factors of 12 and 18. Which of these is the greatest?
6 is the greatest factor that 12 and 18 have in common.


Problem 1
What is the greatest common factor of 8 and 14?
Another way to say this is:
  • Your answer should be
  • an integer, like 6
  • a simplified proper fraction, like 3/5
  • a simplified improper fraction, like 7/4
  • a mixed number, like 1 3/4
  • an exact decimal, like 0.75
  • a multiple of pi, like 12 pi or 2/3 pi

Want to try more problems like this? Check out this exercise.

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