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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 16 hours and 20 hours respectively. If both the pipes are opened simultaneously, how much time will be taken to fill the tank?

    A)  \[8\frac{8}{5}\]hours                

    B)  \[8\frac{8}{9}\] hours    

    C)  \[8\frac{17}{9}\]hours              

    D)  \[8\frac{7}{9}\]hours

    Correct Answer: B

    Solution :

    (b): This again is on the pattern of Q.2; \[\Rightarrow \frac{1}{\frac{1}{16}+\frac{1}{20}}=\frac{16*20}{16+20}\]. \[=\frac{320}{36}=\frac{80}{9}=8\frac{8}{9}\] hours.  


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