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A pipe can fill a cistern in 12 min and another pipe can fill it in 15 min, but a third pipe can empty it in 6 min. The first two pipes are kept open for 5 min in the beginning and then the third pipe is also opened. Time taken to empty the cistern is

A) 38 min
B) 22 min
C) 42 min
D) 45 min

Correct Answer:




D) 45 min

Description for Correct answer:
Let the number of minutes taken to empty the cistern be x min.

According to the question,

\( \Large \frac{x}{6}-\frac{x+5}{12}-\frac{x+5}{12}=0 \)

\( \Large \frac{x}{6}-\frac{x}{12}-\frac{5}{12}-\frac{x}{15}-\frac{5}{15}=0 \)

\( \Large \frac{x}{6}-\frac{x}{12}-\frac{x}{15}=\frac{5}{12}+\frac{5}{15} \)

\( \Large \frac{10x-5x-4x}{60} = \frac{25+20}{60} \)

\( \Large \frac{x}{60} = \frac{45}{60} = x = 45 min. \)

Part of solved Pipes and Cisterns questions and answers : >> Aptitude >> Pipes and Cisterns

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Similar Questions

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