Bhanu Chaudhary
Poll
Professional
Asked: 2022-03-07T14:44:16+05:30

A cistern can be filled with water by a pipe in 5 hours and it can be emptied by a second pipe in 4 hours. If both the pipes are opened when the cistern is full, the time in which it will be emptied the cistern:

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A cistern can be filled with water by a pipe in 5 hours and it can be emptied by a second pipe in 4 hours. If both the pipes are opened when the cistern is full, the time in which it will be emptied the cistern:

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    1 Answer

    1. Professional

      Correct Answer: 20 hours
      1/5+1/4 =4+5/20

      (+) sign shows filling efficiency

      (-) sign shows emptying efficiency

      If A and B work simultaneously. Then A will fill 4 units / hour and B will empty 5 units/hour

      If overall 1 unit/hour will be emptied.

      Then full tank will empty in

      total capacity/A′s eff.+B′s eff.=20/4−5=20/−1

      =20 hours

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