Practice Test Discussion


Pipe A usually fills a tank in 2 hours. On account of a leak at the bottom of the tank, it takes pipe A 30 more minutes to fill the tank. How long will the leak take to empty a full tank if pipe A is shut?

  • Explanation

    Pipe A fills the tank normally in 2 hours
    So, Pipe A can fill half of the tank in 1 hour
    Let us consider, the leak takes x hours to empty the full tank when pipe A is shut.
    So, the leak will empty 1xof the tank in 1 hour.
    The net amount of water that gets filled in the tank in 1 hour when pipe A and the leak are open=12-1x of the tank---Eq 1

    As per the question,
    when the leak is open, time taken to fill the tank =212=52 hours

    Therefore, in 1 hour, 25th of the tank gets filled--Eq 2

    Equating Eq1 and Eq2, we get

    12-1x=251x=12-25 =1101x=110x=10 hours

    Hence option D is correct. 

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