Question : Pipe P alone can fill a tank in 18 hours and Pipe Q alone can fill the same tank in 24 hours. If both the pipes are opened on alternate hours one at a time and pipe Q is opened for the first hour, then in how much time the tank will be full?
Option 1:
Option 2:
Option 3:
Option 4:
Correct Answer:
Solution :
According to the question,
Pipe P fills the tank in 18 hours, so its rate =
Pipe Q fill tank in 24 hours, so its rate =
⇒ Combined rate
So, in 2 hours, if both work alternatively starting with Q, the amount of work done =
Thus, in 20 hours, the amount of work done =
⇒ Remaining work = 1 –
⇒ Time taken by Q to finish the remaining work =
So, the total time
Hence, the correct answer is