A can do a work in 30 days, B can do the same work in 45 days, and C can do it in 60 days. If they work together, how long will they take to complete the work?
Answer: B. 12 days
Their combined work rate is 1/30 + 1/45 + 1/60 = 1/12. Therefore, they will complete the work in 12 days.