Pipes and Cistern

  1. Pipe A can fill a tank in 45 hrs and pipe B can fill it in 36 hrs. If both the pipes are opened in the empty tank. In how many hours will it be full?
    1. 10 hr
    2. 15 hr
    3. 20 hr
    4. 28 hr
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    Part filled by A in 1 hr= (1/45)
    Part filled by B in 1 hr= (1/36)

    Correct Option: C

    Part filled A in 1 hr= (1/45)
    Part filled B in 1 hr= (1/36)
    Part filled by (A+B) together in 1 hr=(1/45)+(1/36)=1/20

    So, The tank will be full in 20 hr.

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  1. If a pipe fills a tank in 6 h, then what part of the tank will the pipe fill in 1 h?
    1. 1/3
    2. 1/6
    3. 1/4
    4. 1/5
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    We know that, when a pipe fills a tank in m h, then the part of tank filled in 1 h = 1/m

    Correct Option: B

    We know that, when a pipe fills a tank in m h, then the part of tank filled in 1 h = 1/m
    Here, m = 6
    ∴ Required part of the tank to be filled in 1h = 1/6 part

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  1. A pipe can empty a tank in 12 minutes and another pipe can empty it in 16 minutes. If both the pipes are opened simultaneously, find the time in which a full tank is emptied ?
    1. 6 minutes
    2. 61/7 minutes
    3. 62/7 minutes
    4. None of these
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    Required answer = (12 x 16) /(12 + 16) = 48 / 7 = 66/7 minutes.

    Correct Option: D

    Required answer = (12 x 16) /(12 + 16) = 48 / 7 = 66/7 minutes.

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  1. An inlet pipe fills 1/8 part of a tank in 1 h. How much time will the pipe take to fill the empty tank ?
    1. 4 h
    2. 2 h
    3. 6 h
    4. 8 h
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    When a pipe fills 1/m part of a tank in 1 h, then the pipe takes m h to fill the tank.

    Correct Option: D

    We know that, when a pipe fills 1/m part of a tank in 1 h, then the pipe takes m h to fill the tank.
    Here, 1/m = 1/8 ⇒ m = 8
    ∴ Required time to fill the tank = 8 h

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  1. An outlet pipe can empty a cistern in 3 h. In what time will the pipe empty two-third part of the cistern?
    1. 4 h
    2. 2 h
    3. 3 h
    4. 5 h
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    Time taken by the pipe to empty the cistern = 3 h
    Then, time taken by the pipe to empty the 2/3 part = 3 x 2/3 = 2 h

    Correct Option: B

    Time taken by the pipe to empty the cistern = 3 h
    Then, time taken by the pipe to empty the 2/3 part = 3 x 2/3 = 2 h

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