P is four times as fast as Q and working together, they can complete a work in 15 days. In how many days can Q alone complete the work?  Choose the correct choice from the following answers.
A) 5 1/4 days B) 8 3/4 days C) 16 1/4 days D) 25 days E) 18 days
P = 4Q   P + Q = 4Q + Q = 5Q   These 5Q people can do the work in 15 days, which means Q can do the work in 75 days.   Hence, P can do the work in 18 3/4 days.   ANSWER:8 3/4 days
<result>B</result>
P is four times as fast as Q and working together, they can complete a work in 15 days. In how many days can Q alone complete the work?