What is the greatest common factor of 16 and 80?

Answer 1

I know that 16 x 5 = 80, so the greatest common factor of 16 and 80 must be 16, since the greatest common factor cannot be larger than the small number. But, if you did not know this, you would need to compare their factors.

The factors of 16 are 1, 2, 4, 8, and 16.

The factors of 80 are 1, 2, 4, 5, 8, 10, 16, 20, 40, and 80.

The largest of the factors they have in common is 16, so 16 is the greatest common factor.

Or, you can determine the greatest common factor by their prime factors.

The prime factors of 16 are 2, 2, 2, and 2.

The prime factors of 80 are 2, 2, 2, 2, and 5.

The prime factors they have in common are four 2s, so 2 x 2 x 2 x 2 = 16 is the greatest common factor.

Answer 2

The GCF is 16.