A tap can fill a tank in 4 hours. After half the tank is filled three more similar taps are opened. What is the total time taken to fill the tank completely?  Pick.
A) 3 hrs 45 min
B) 3 hrs 50 min
C) 3 hrs 12 min
D) 3 hrs 30 min
E) 3 hrs 22 min
Time taken by one tap to fill the tank = 2 hrs.   Part filled by the taps in 1 hour = 4 * 1/4= 
<gadget id="calculator">4 * 1/4</gadget>
<output>1</output>
1   Remaining part= 1 - 1/2 = 1/2   1 : 1/2 :: 1 : x   x = 1/2 * 1 * 1 = 1/2 hrs. i.e., 30 min   So, total time taken = 3 hrs 30 min.   ANSWER: 3 hrs 30 min
<result>D</result>
A tap can fill a tank in 4 hours. After half the tank is filled three more similar taps are opened. What is the total time taken to fill the tank completely?