8th Class Mathematics Direct and Inverse Proportions Question Bank Direct and Inverse Proportions

  • question_answer A photograph of a bacteria enlarged 50,000 times, attains a length of 5 cm. What is the actual length of the bacteria?

    A)  \[2\times {{10}^{-4}}cm\]              

    B)  \[{{10}^{3}}cm\]   

    C)  \[{{10}^{-4}}cm\]  

    D)         \[{{10}^{4}}\text{ }cm\]    

    Correct Answer: C

    Solution :

    Let actual length of bacteria be \[x\] cm.
    Enlargement of the photograph 50,000 times 1 time
    Length of bacteria 5 cm X
    More the enlargement of photograph, more would be its length. So, it is a case of direct proportion. Hence, \[\frac{50000}{5}=\frac{1}{x}\Rightarrow x=\frac{5}{50000}={{10}^{-4}}cm\].


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