Question: is 80 multiple of 20?
Answer: The multiples of 20 are … , 60, 80, 100, …. The multiples of 80 are …, 0, 80, 160, … The common multiples of 20 and 80 are n x 80, intersecting the two sets above, n ϵ Z . In the intersection multiples of 20 ∩ multiples of 80 the least positive element is 80.