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

  • question_answer
    The ratio of areas of incircle and circumcircle of an equilateral triangle is:

    A) \[1:2\]

    B) \[1:3\]

    C) \[1:4\]

    D) \[1:9\]

    Correct Answer: C

    Solution :

    [c] Let side of equilateral triangle = x units
    \[\therefore \] Altitude \[=\frac{\sqrt{3}}{2}=x\] units
    Radius of in circle  \[=\frac{1}{3}\times \frac{\sqrt{3}}{2}\times \text{units}\]
                            \[=\frac{\sqrt{3}}{6}\times \text{units}\]
    Radius of circumcircle
                \[=\frac{2}{3}\times \frac{\sqrt{3}}{2}\times \text{units=}\frac{\sqrt{3}}{3}\times \text{units}\]
    \[\therefore \frac{\text{Area of incircle}}{\text{Area of circumcircle}}=\frac{\pi {{\left( \frac{\sqrt{3}}{6}x \right)}^{2}}}{\pi {{\left( \frac{\sqrt{3}}{3}x \right)}^{2}}}\frac{9}{36}=\frac{1}{4}=1:4\]


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