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7th Class Mental Ability Numbers Question Bank Number System

  • question_answer
    A container is filled with a liquid up to \[\frac{\mathbf{4}}{\mathbf{5}}\]th of its volume. When 6 bottles of liquid are taken out and four bottles of liquid are poured back into it. It is \[\frac{\mathbf{3}}{\mathbf{4}}\]th of the volume. Find the number of bottles of liquid in the container when the container is full.

    A) 15                   

    B)   40

    C) 39                 

    D)   33

    E) None of these

    Correct Answer: B

    Solution :

    Explanation Liquid into container \[=\,\,\frac{4}{5}\,\,x\]. Let a bottle contains y litre. The amount of liquid left in the container after 6 bottles are taken out and 4 bottles are poured back into it. According to question, \[\frac{4}{5}\,x-6y+4y=\frac{3}{4}x\,\,\Rightarrow \,\,\frac{4}{5}x-2y=\frac{3}{4}x\] \[\Rightarrow \,\,\,2y=\frac{4}{5}\,x-\frac{3}{4}x\,\,\Rightarrow \,2y=\,\frac{1}{20}x\,\,\Rightarrow \,\,y=\frac{x}{\frac{1}{40}x}\] The number of bottles required to completely empty the container is 40.


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