Question: what is a common factor of 11 and 32?
Answer: The factors of 32 are 32, 16, 8, 4, 2, 1. The common factors of 11 and 32 are 1, intersecting the two sets above. In the intersection factors of 11 ∩ factors of 32 the greatest element is 1. Therefore, the greatest common factor of 11 and 32 is 1.