P is four times as fast as Q and working together, they can complete a work in 12 days. In how many days can Q alone complete the work? Choose one: A) 35 days B) 15 days C) 16 days D) 25 days E) 18 days
P = 4Q   P + Q = 4Q + Q = 5Q   These 5Q people can do the work in 12 days, which means Q can do the work in 60 days.   Hence, P can do the work in 15 days.   ANSWER:15 days
<result>B</result>
P is four times as fast as Q and working together, they can complete a work in 12 days. In how many days can Q alone complete the work?