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Practice mode Pipes and Cistern

A cistern is 3/4 full. An outlet can empty the full cistern in 12 minutes and an inlet can fill it in 18 minutes. If both are opened, how long will the cistern take to empty?

Correct answer B. 27 minutes

Explanation

Net emptying rate = 1/12 − 1/18 = 1/36 per minute. Emptying 3/4 takes 3/4 × 36 = 27 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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