Correct Answer - Option 3 : 13
\(\frac{1}{2}\) minutes
Given:
Pipes A and B can fill a tank in 18 minutes and 27 minutes, respectively.
When A, B and C are opened together, the empty tank is completely filled in 54 minutes.
Calculation:
Pipe A's 1 minute's work = 1/18
Pipe B's 1 minute's work = 1/27
Let pipe C's 1 minute's work be 1/C.
⇒ (1/18 + 1/27) - 1/C= 1/54
⇒ 1/C = 2/27
∴ Pipe C can alone empty the tank in 27/2 = 13\(\frac{1}{2}\) minutes.
When a pipe is emptying the tank then it is considered as negative work.