A water tank is one-third full. Pipe A can fill a tank in 10 minutes and pipe B can empty it in 6 minutes. If both the pipes are open, how long will it take to empty or fill the tank completely?
Select
A) 5 min. to empty	B) 6 min. to full	C) 9 min. to empty	D) 9 min. to full	E) 8 min. to full
Clearly, pipe B is faster than pipe A and so, the tank will be emptied.   Part to be emptied = 1/3   Part emptied by (A + B) in 1 minute = (1/6 - 1/10) = 1/15   1/15 : 1/3 :: 1 : x   x = (1/3 * 1 * 15)= 
<gadget id="calculator">(1/3 * 1 * 15)</gadget>
<output>5</output>
5 min.   So, the tank will be emptied in 5 min.   5 min. to emptyNSWER:5 min. to empty
<result>A</result>
A water tank is one-third full. Pipe A can fill a tank in 10 minutes and pipe B can empty it in 6 minutes. If both the pipes are open, how long will it take to empty or fill the tank completely?