A water tank is two fifth 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?
সমাধান
সঠিক উত্তর: Option A
Clearly, pipe B is faster than pipe A and so, the tank will be emptied. Part to be emptied = 2/5 Part emptied by (A + B) in 1 minute = 1/6 - 1/10 = 1/15 ∴ 1/15 : 2/5 :: 1 : x ⇒ x = 2/5 ×1 ×15 = 6 So, tank will be emptied in 6 min.
