A tap can fill a tank in 6 hours. After half the tank is filled, three other taps of the same efficiency are opened. How much time will it take to fill the tank completely?
A
2 hours 30 minutes
B
2 hours 45 minutes
C
3 hours 30 minutes
D
3 hours 45 minutes
Correct Option:
D
Explanation
One tap fills half the tank in 3 hours. Then four identical taps operate together. Their combined rate is 4/6 = 2/3 of a tank per hour. Half a tank therefore needs (1/2) ÷ (2/3) = 3/4 hour = 45 minutes. Total time = 3 hours 45 minutes.
