A tap can fill a tank in 4 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 most appropriate option:
A) 1 hr 20 min
B) 4 hr
C) 3 hr
D) 2 hr 40 min
E) 2 hr 50 min
Explanation:   1 tap can fill the tank in 4 hours.   Therefore   1 tap can fill half tank in 2 hours.   3 taps can fill the tank in 4/3 hour.   Therefore   3 taps can fill half tank in 4/6 hour =40 minutes.   Total time taken=2 hour 40 minutes   Answer: Option 2 hr 40 min
<result>D</result>
A tap can fill a tank in 4 hours. After half the tank is filled, two more similar taps are opened. What is the total time taken to fill the tank completely?