What is the greatest common factor of 12 and 90?

Answer 1

The factors of 12 are 1, 2, 3, 4, 6, and 12.

The factors of 90 are 1, 2, 3, 5, 6, 9, 10, 15, 18, 30, 45, and 90.

The common factors are 1, 2, 3, and 6, so the greatest common factor is 6.

You can also determine this from the prime factors.

The prime factors of 12 are 2, 2, and 3.

The prime factors of 90 are 2, 3, 3, and 5.

The prime factors they have in common are 2 and 3, so the greatest common factor is 2 x 3 = 6.