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 option:
A) 3 hrs 15 min	B) 3 hrs 45 min	C) 4 hrs	D) 4 hrs 15 min	E) 4 hrs 45 min
time taken by one tank to fill half the tank=4*(1/6)   Part filled by the four taps in 1 hour=4*(1/6)   remaining part=1/2   therefore 2/3:1/2::1:x   x=3/4hr=(3/4)*60= 
<gadget id="calculator">(3/4)*60</gadget>
<output>45</output>
45min   total time=3 hr 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 ?