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

  • question_answer
    The ratio of the outer and inner circumference of a circular path is\[\text{23}:\text{22}\]. If the path is 5 meters wide, the diameter of the inner circle is:

    A) \[55\,m\]

    B) \[110\,m\]

    C) \[220\,m\]

    D) \[230\,m\]

    Correct Answer: C

    Solution :

    [c] Let \[{{R}_{1}}\] and \[{{R}_{2}}\] be the radii of outer and inner circular path respectively.
    \[\therefore \,\,\,\,\,\,\,\,\,\,\,\,\frac{2\pi {{R}_{1}}}{2\pi {{R}_{2}}}=\frac{23}{22}\]
    \[\Rightarrow \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\frac{{{R}_{1}}}{{{R}_{2}}}=\frac{23}{22}\,\,\,\,\,\,\,\Rightarrow \,\,{{R}_{1}}=\frac{23}{22}{{R}_{2}}\]           …(1)
    Also,\[{{R}_{1}}-{{R}_{2}}=5\,\,\,\,\Rightarrow \,\,\,\frac{23}{22}{{R}_{2}}-{{R}_{2}}=5\](Using (1))
    \[\Rightarrow \,\,\,\,\,\,\,\,\,\,\,\,\,{{R}_{2}}=5\times 22=110m\]
    \[\therefore \] Diameter of inner circle       \[=2{{R}_{2}}=(2\times 110)\,m=220m\]


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