X can do a piece of work in 15 days. If he is joined by Y who is 50% more efficient, in what time will X and Y together finish the work?
Choose the correct choice from the following
A) 10 days
B) 6 days
C) 18 days
D) Data insufficient
E) None of these
X’s one day’s work = 1⁄15 th work.   Y’s one day’s work = 1⁄15 + 50% of 1⁄15 = 1⁄10 th work.   ∴ (X + Y)’s one day’s work = 1⁄15 + 1⁄10 = 1⁄6 th work.   Hence, they together finish the work in 6 days.   Answer 6 days
<result>B</result>
X can do a piece of work in 15 days. If he is joined by Y who is 50% more efficient, in what time will X and Y together finish the work?