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Pipes A and B can fill a tank in 18 minutes and 27 minutes, respectively. C is an outlet pipe. When A, B and C are opened together, the empty tank is completely filled in 54 minutes. Pipe C alone can empty the full tank in:1. 14\(\frac{1}{2}\) minutes2. 14 minutes3. 13\(\frac{1}{2}\) minutes4. 13 minutes |
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Answer» 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. |
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