Question: what is the highest common factor between 6 and 27?
Answer: The factors of 27 are 27, 9, 3, 1. The factors of 6 are 6, 3, 2, 1. The common factors of 27 and 6 are 3, 1, intersecting the two sets above. In the intersection factors of 27 ∩ factors of 6 the greatest element is 3. Therefore, the greatest common factor of 27 and 6 is 3.