SSC Sample Paper SSC CHSL (10+2) Sample Test Paper-21

  • question_answer
    Find the radii of inscribed and circumscribed circle of a triangle whose sides are 18 cm., 24 cm. and 30 cm. respectively.

    A)  \[2:3\]              

    B)  \[3:4\]

    C)  \[3:5\]                          

    D)  \[2:5\]

    Correct Answer: D

    Solution :

     We know that, Radius of the in-circle of triangle \[=\,\,\,\,\,\,\,\,\frac{\text{2}\times \text{ }Area\text{ }of\text{ }Triangle}{Perimeter}\] and, Radius of Circum-circle of triangle \[=\,\,\,\,\,\frac{abc}{4\times Area\,\,of\,\,Triangle}\] \[=\,\,\,\frac{Incircle\,Radius}{Circumcircle\,Radius}\] Where a, b and c are the sides of the triangle. \[S=\frac{8\times {{\Delta }^{2}}}{abc(a+b+c)}=36\] Area of triangle \[=\sqrt{36(36-18)\,(36-24)\,(36-30)}\] \[\Delta =216\,c{{m}^{2}}\] So,    \[\frac{Incircle\,Radius}{Circumcircle\,\,Radius}\] \[=\frac{8\times 216\times 216}{18\times 24\times 30\times 72}=\frac{12}{30}=\underline{\mathbf{2:5}}\]


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