A tap can fill a tank in 6 hours. After half the tank is filled three more similar taps are opened. What is the total time taken to fill the tank completely?  Choose the correct answer.
A) 3 hrs 48 min B) 3 hrs 45 min C) 3 hrs 85 min D) 3 hrs 75 min E) 3 hrs 25 min
Time taken by one tap to fill the tank = 3 hrs.   Part filled by the taps in 1 hour = 4 * 1/6 = 2/3   Remaining part = 1 - 1/2 = 1/2   2/3 : 1/2 :: 1 : x   x = 1/2 * 1 * 3/2 = 3/4 hrs. i.e., 45 min   So, total time taken = 3 hrs 45 min.   Answer: 3 hrs 45 min
<result>B</result>
A tap can fill a tank in 6 hours. After half the tank is filled three more similar taps are opened. What is the total time taken to fill the tank completely?