Is 1 the greatest common factor of 42 and 90?

Answer 1

No, it is 6.

The factors of 42 are 1, 2, 3, 6, 7, 14, 21, and 42.

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 by looking at the prime factors.

The prime factors of 42 are 2, 3, and 7.

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.