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11th Class Mental Ability Arithmetic Question Bank Question - Arithmetic

  • question_answer
    Two fill pipes A and B can fill a cistern in 12 and 16 minutes respectively. Both fill pipes are opened together, but 4 minutes before the cistern is full, one pipe A is closed. How much time will the cistern take to fill?

    A) \[9\frac{1}{4}minutes\]

    B) \[3\frac{1}{3}minutes\]

    C) 5 minutes

    D) 3 minutes

    E) None of these

    Correct Answer: A

    Solution :

    Explanation Option (a) is correct. Let cistern will be will be full in x min. then, part filled by B in x min + part filled by A in (x - 4) min = 1 \[\Rightarrow \frac{x}{16}+\frac{x-4}{12}=1\] \[\Rightarrow x=\frac{64}{7}=9\frac{1}{7}min.\]


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