Question: is 25 a multiple of 20?
Answer: The multiples of 20 are … , 80, 100, 120, …. The multiples of 25 are …, 75, 100, 125, … ... In the intersection multiples of 20 ∩ multiples of 25 the least positive element is 100. Therefore, the least common multiple of 20 and 25 is 100.