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Practice mode Pipes and Cistern

Pipes A and B can fill a tank in 20 and 30 minutes respectively. Both are opened together, but A is turned off 5 minutes before the tank is full. How long does the tank take to fill?

Correct answer A. 15 minutes

Explanation

If total time is t, then (t − 5)/20 + t/30 = 1. So 3t − 15 + 2t = 60, giving t = 15 minutes.

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Question 03 Pipes and Cistern

How long will it take to empty the tank if both the inlet pipe A and the outlet pipe B are opened simultaneously? I. A can fill the tank in 16 minutes. II. B can empty the full tank in 8 minutes.

Correct answer B. II alone sufficient while I alone not sufficient to answer

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Question 04 Pipes and Cistern

How much time will the leak take to empty the full cistern? I. The cistern is normally filled in 9 hours. II. It takes one hour more than the usual time to fill the cistern because of la leak in the bottom.

Correct answer B. II alone sufficient while I alone not sufficient to answer

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