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8th Class Mathematics Comparing Quantities Question Bank Percentage, Profit and Loss

  • question_answer
    The price of a commodity is increased by 40%. By what per cent should a consumer reduce his consumption so that his expenditure on the commodity remains constant?

    A)  \[25\frac{4}{7}%\]                   

    B)  \[26\frac{4}{7}%\]

    C)  \[27\frac{4}{7}%\]                   

    D)  \[28\frac{4}{7}%\]

    Correct Answer: D

    Solution :

    (d): Let him consume 'x' kg previously Previous price = C Rs/kg \[\Rightarrow \text{cost}=xC\] New price = 1.4C Rs/kg. Let new consumption decrease by p%. \[\Rightarrow New\text{ }consumption=\frac{x(100-p)}{100}kg\] \[\therefore New\,cost=\frac{x\left( 100-p \right)}{100}\times \left( 1.4C \right)\] \[\therefore \frac{x\left( 100-p \right)}{100}\times \left( 1.4C \right)=xC\] \[\Rightarrow 1.4(100-p)=100\] \[\Rightarrow 140-1.4=100\] \[\Rightarrow 40=1.4p\] \[\Rightarrow p=\frac{40}{1.4}=\frac{40\times 5}{7}=\frac{200}{7}=28\frac{4}{7}%\]


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