Question: is 12 a common factor of 20 and 36?
Answer: The factors of 20 are 20, 10, 5, 4, 2, 1. The factors of 36 are 36, 18, 12, 9, 6, 4, 3, 2, 1. The common factors of 20 and 36 are 4, 2, 1, intersecting the two sets above. ... Therefore, the greatest common factor of 20 and 36 is 4.