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