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8th Class Mathematics Direct and Inverse Proportions Question Bank Direct & Inverse Proportional (Time & Work)

  • question_answer
    Two pipes A and B can fill a tank in 24 hours and 30 hours respectively. The tank is emptied. How much time will be taken by them to fill it?

    A)  13 hours 20 min.

    B)  16 hours 30 min.

    C)  14 hours 10 min.          

    D)  15 hours 40 min.

    Correct Answer: A

    Solution :

    (a): By logic of Q-2, we get Time \[=\frac{1}{\frac{1}{24}+\frac{1}{30}}=\frac{24\times 30}{24+30}\] \[=\frac{24\times 30}{54}=\frac{240}{18}=\frac{40}{3}\] = 13 hrs.20min.


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