9th Class Mathematics Related to Competitive Exam Question Bank Arithmetic

  • question_answer
    A tyre has two punctures. The first puncture alone would have made the tyre flat in 9 minutes and the second alone would have done it in 6 minutes. If air leaks out at a constant rate, then how long does it take both the punctures together to make it flat?

    A) \[3\frac{1}{5}\] min       

    B)        \[3\frac{2}{5}\] min

    C) \[3\frac{3}{5}\] min    

    D)        \[3\frac{4}{5}\] min

    E) None of these

    Correct Answer: C

    Solution :

    Explanation Option [c] is correct. Do not be confused, take this question same as that of work done question's. Like work done by 1st puncture in 1 minute and by second in 1 minute. Lets solve it: 1 minute work done by both the punctures \[=\left( \frac{1}{9}+\frac{1}{6} \right)=\left( \frac{5}{18} \right)\] So both punctures will make the type flat in \[\left( \frac{18}{5} \right)\] mins \[=3\frac{3}{5}\]        


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