What is the greatest common factor of 45 and 55?

Answer 1

10

Answer 2

The greatest common factor of 45 and 55 is 5

To determine GCF you first find the prime factors of each number.

For 45 this is (5, 3, 3).

For 55 this is (11, 5).

Then you take the product of the prime factors that they have in common. In this case the only prime factor they have in common is 5 so the answer is just 5.

For a better illustration of the rule look at 45 and 30.

Prime factors of 45 are (5, 3, 3)

Prime factors of 30 are (5, 3, 2)

The prime factors in common are 5 and 3 and the product of these numbers is 15. Therefore the GCF of 45 and 30 is 15.

Answer 3

55 = 5 x 11

45 = 5 x 3 x3

GCF = 5