JEE Main & Advanced Mathematics Circle and System of Circles Question Bank Equations of circle, Geometrical problems regarding circle

  • question_answer
     If a circle and a square have the same perimeter, then  [Pb. CET 2001]

    A)            Their area are equal

    B)            Area of circle is larger

    C)            Area of square is larger

    D)            None of these

    Correct Answer: B

    Solution :

               We are given that, the perimetre of the circle is equal to the perimetre of square.                    \[\therefore \] Let ?r? be the radius of circle and ?a? be the side of square                    \[\therefore \]  \[2\pi \,r=4a\Rightarrow a=\frac{\pi \,r}{2}\]                    \[\therefore \] Area of square \[\Rightarrow \] \[{{a}^{2}}=\frac{{{\pi }^{2}}{{r}^{2}}}{4}\]                    and area of circle = \[\pi \,{{r}^{2}}\]                    \[\therefore \] \[\frac{\text{Area of circle}}{\text{Area of square}}=\frac{\pi \,{{r}^{2}}}{{{\pi }^{2}}{{r}^{2}}/4}=\frac{4}{\pi }>1\].                    Thus, area of circle is larger than area of square.


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