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Discussion :: Pipes and Cistern

  1. Two pipes can fill a tank in 20 and 24 minutes respectively and a waste pipe can empty 3 gallons per minute. All the three pipes working together can fill the tank in 15 minutes. The capacity of the tank is:

  2. A.

    60 gallons

    B.

    100 gallons

    C.

    120 gallons

    D.

    180 gallons

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    Answer : Option C

    Explanation :

    = [\(\frac { 1 } { 15 }-\)\(\frac { 11 } { 120 }]\)

     

    =- \(\frac { 1 } { 40 }\). [-ve sign means emptying

     

     Volume of\(\frac { 1 } { 40 }\) Part =3 gallons

     

    Volume of whole = (3 x 40) gallons = 120 gallons.

     

     

    Work done by the waste pipe in 1 minute = \(\frac { 1 } { 15 }-\)[\(\frac { 1 } { 20 }+\)\(\frac { 1 } { 24}]\)


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