When dealing with abstract numbers, you can multiply any number by any fraction. However, doing so doesn't always make sense when using real objects like people. For instance, there can't be 10 people in this club; if 2/3 of the people ordered a drink, that would be 6 2/3 people who ordered drinks. If 2/3 ordered a drink, that means the number of people in the club must be a multiple of 3, such as 6 or 9. The same reasoning applies to 1/4 and 2/5 -- the number of people in the club must be a multiple of 4 and a multiple of 5. Thus, we're looking for the least common multiple of 3, 4, and 5. Since those numbers don't have any factors in common, the LCM is the product: 3(4)(5) = 60. Since the LCM is 60, the number of people in the club must be 60 or a multiple of 60. The only acceptable answer is (E), 120, which is a multiple of 60.