A tap can fil up an empty tank in 5 hours wheras it can be emptied by a pipe in 6 hours. How long will it take to fill the empty tank if both the taps and pipe are opened together?	Choices
A) 40 hrs. B) 30 hrs. C) 50 hrs. D) 60 hrs. E) 20 hrs.
Explanation:   In this type of questions we first get the filling in 1 minute for both pipes then we will add them to get the result, as   Part filled by rap in 1 hr= 1/5   Part emptied by pipe in 1 hr= 1/6   work done by (tap+pipe) in 1 hr= 1/5 - 1/6   = 1/30   So both tap and pipe opened the tank will fill in 30 hrs.   Option 30 hrs.
<result>B</result>
A tap can fil up an empty tank in 5 hours wheras it can be emptied by a pipe in 6 hours. How long will it take to fill the empty tank if both the taps and pipe are opened together?