Best Answer

9 is a factor of both 18 and 45, and is the largest factor of itself, so 9 is the greatest common factor.

One way to determine the greatest common factor is to find all the factors of the numbers and compare them.

The factors of 9 are 1, 3, and 9.

The factors of 18 are 1, 2, 3, 6, 9, and 18.

The factors of 45 are 1, 3, 5, 9, 15, and 45.

The common factors are 1, 3, and 9. Therefore, 9 is the greatest common factor.

The greatest common factor can also be calculated by identifying the common prime factors and multiplying them together.

The prime factors of 9 are 3 and 3.

The prime factors of 18 are 2, 3, and 3.

The prime factors of 45 are 3, 3, and 5.

The prime factors they all have in common are 3 and 3, so the greatest common factor is 3 x 3 = 9.

WHAT? evry gcf # has to be PRIME only? HELP!!!!!!!!

Q: What is the greatest common factor of 9 18 and 45?

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