Question

Which of the following is a factor of 90 but not a factor of 75?

Answer 1

Factors of 90 are: 1, 2, 3, 5, 6, 9, 10, 15, 18, 30, 45, 90.
Factors of 75 are: 1, 3, 5, 15, 25 and 75.
Factors of 30 are: 1, 2, 3, 5, 6, 10, 15 and 30
So, 30 is a factor of 90 but not a factor of 75.
Hence the right answer is 30.