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

  • question_answer
    In 15 days, the earth picks up \[1.2\times {{10}^{8}}\text{kg}\] of dust from the atmosphere. In how many days it will pick up \[4.8\times {{10}^{8}}\text{ kg}\]of dust?

    A)  50                              

    B)         40      

    C)         60                              

    D)         100

    Correct Answer: C

    Solution :

    Number of days 15 x
    Weight of dust (in kg) \[1.2\times {{10}^{8}}\] \[4.8\times {{10}^{8}}\]
    More the dust, more the number of days it will take to pick it up. So, it is a case of direct proportion. \[\therefore x=\frac{15}{1.2\times {{10}^{8}}}\times 4.8\times {{10}^{8}}days\] \[\Rightarrow x=\frac{15\times 4.8}{1.2}=60days\]


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