arithmetic - a tap can fill a tank in 9 hours after half the tank is filled two more similar taps are opened what is the total time taken to fill the tank completely - skillgun

Solution: Time taken by one tap to fill the tank = 9/2 = 4.5 hours. ('.' since given it will take 9 hours to fill the tank completely)
Part filled by the three taps in 1 hour =(3* 1/9) = 1/3.
Remaining part = (1 - 1/2) = 1/2.
.'. 1/3 part in 1 hour, then, 1/2 part in = 1/2 * 1 * 3/1 = 3/2 = 1/5 hours.
So, total time taken = 4.5+1.5 = 6 hours.