is twice as fast as B. If B alone can do a piece of work in 30 days, in what time can A and B together complete the work?
Choose the correct choice from the following answers
A) 13 days B) 10 days C) 16 days D) 11 days E) 18 days
B   10 days   A can do the work in 30/2 i.e., 15 days.   A and 10 days's one day's work = 1/15 + 1/30 = (2 + 1)/30 = 1/10   So A and 10 days together can do the work in 10 days.
<result>B</result>
is twice as fast as B. If B alone can do a piece of work in 30 days, in what time can A and B together complete the work?