A Cistern is filled by pipe A in 9 hrs and the full Cistern can be leaked out by an exhaust pipe B in 10 hrs. If both the pipes are opened in what time the Cistern is full? Choose the correct option
A) 45  B) 90  C) 1/10  D) 1/90  E) 60
Explanation :   Work down by the inlet in 1 hr = 1 /9   Work done by outlet in 1 hr 1/10   Net part filled in 1 hr = 1/9 - 1/10 = 1/90   The Cistern will be full in 90 hrs.   Hint: Take the reciprocals.   Answer : 90
<result>B</result>
A Cistern is filled by pipe A in 9 hrs and the full Cistern can be leaked out by an exhaust pipe B in 10 hrs. If both the pipes are opened in what time the Cistern is full?