A tap can fill a tank in 6 hours. After half the tank is filled, two more similar taps are opened. What is the total time taken to fill the tank completely? Choose the correct choice:
A) 1 hr 20 min
B) 2 hr
C) 3 hr
D) 4 hr
E) 5 hr 50 min
Explanation:   1 tap can fill the tank in 6 hours.   Therefore   1 tap can fill half tank in 3 hours.   3 taps can fill the tank in 6/3= 
<gadget id="calculator">6/3</gadget>
<output>2</output>
2 hours.   Therefore   3 taps can fill half tank in 2/2 hour=60 minutes = 1hour.   Total time taken=4 hours   Answer: Option 4 hr
<result>D</result>
A tap can fill a tank in 6 hours. After half the tank is filled, two more similar taps are opened. What is the total time taken to fill the tank completely?