10th Class Mathematics Areas Related to Circles Question Bank MCQs - Areas Related to Circles

  • question_answer
    The sum of radii of two different wheels of a tractor is \[\text{98 cm}\] and the difference of their circumferences is\[\text{176 cm}\]. Find the diameter of the bigger wheel.

    A) \[\text{128 cm}\]

    B) \[\text{126 cm}\]

    C) \[\text{63 cm}\]

    D) \[\text{64 cm}\]

    Correct Answer: B

    Solution :

    [b] Let \[{{r}_{1}}\,cm\] and \[{{r}_{2}}\,cm\] be the radii of smaller and bigger wheels of the tractor respectively.
    \[\therefore \,\,\,\,\,\,\,\,\,\,\,\,\,{{r}_{1}}+{{r}_{2}}=98\]    ...(1)
    Also,  \[2\pi {{r}_{2}}-2\pi {{r}_{1}}=176\]
    \[\Rightarrow \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,{{r}_{2}}-{{r}_{1}}=\frac{176}{2\pi }=\frac{176\times 7}{2\times 22}=28\]       ...(2)
    Adding (1) and (2), we have
    \[2{{r}_{2}}=126\,\,\,\,\Rightarrow \,\,{{r}_{2}}=63\]
    \[\therefore \] Diameter of bigger wheel
    \[=(2\times 63)cm=126cm\]


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