A is twice as fast as B. If B alone can do a piece of work in 18 days, in what time can A and B together complete the work?
Choose the correct choice
A) 10	B) 16	C) 18	D) 6	E) 12
A can do the work in 18/2 i.e., 9 days.   A and B's one day's work = 1/9+ 1/18 = (2 + 1)/18 = 1/6   So A and B together can do the work in 6 days.   Answer: 6
<result>D</result>
A is twice as fast as B. If B alone can do a piece of work in 18 days, in what time can A and B together complete the work?