Question: what number is not a common factor of 24 and 36?
Answer: The gcf of 24 and 36 can be obtained like this: The factors of 24 are 24, 12, 8, 6, 4, 3, 2, 1. The factors of 36 are 36, 18, 12, 9, 6, 4, 3, 2, 1. The common factors of 24 and 36 are 12, 6, 4, 3, 2, 1, intersecting the two sets above.