If A, B, and C can complete a piece of work in 12, 15, and 20 days respectively, in how many days can they together complete the work?
Answer: B
Total work can be assumed as the LCM of 12, 15, and 20, which is 60 units. A's efficiency = 60/12 = 5 units/day. B's efficiency = 60/15 = 4 units/day. C's efficiency = 60/20 = 3 units/day. Together, their efficiency = 5+4+3 = 12 units/day. Time taken to complete the work together = Total work / Combined efficiency = 60 / 12 = 5 days.