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Q: Each inlet pipe can fill an empty cistern in the 84 hours while each outlet pipe can empty the same cistern from a filled condition in 105 hours. When the cistern is empty , 9 inlet pipes and 10 outlet pipes are simultaneously opened . After how many hours will the cistern be completely filled?
  • A. 90
  • B. 88
  • C. 80
  • D. 84
Correct Answer: Option D -
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Explanations:

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