A can do a work in 16 days and B can do it in 24 days. If they work together for 8 days, how much of the work is left?
Answer: C. 1/2
A's rate is 1/16 and B's rate is 1/24. Together, they complete 1/16 + 1/24 = 5/48 of the work in a day. In 8 days, they complete 40/48 = 5/6 of the work, leaving 1/6 of the work.