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

  • question_answer
    In given figure, ABC is a triangle right- angled at B, with AB = 14 cm and BC = 24 cm. With the vertices A, B and C as centres, arcs are drawn each of radius 7 cm. Find the area of the shaded region. [Use \[\pi =\frac{22}{7}\]]                        

    A)  \[91\text{ }c{{m}^{2}}\]                

    B) \[95\,c{{m}^{2}}\]             

    C)                                 \[97\,c{{m}^{2}}\]            

    D)       \[88\,c{{m}^{2}}~\]      

    Correct Answer: A

    Solution :

    Area of \[\Delta \,ABC=\frac{1}{2}\times AB\times BC\] \[=\frac{1}{2}\times 14\times 24=168c{{m}^{2}}\] Area of sector centred at                         \[A=\frac{\angle A}{{{360}^{o}}}\times \pi {{(7)}^{2}}c{{m}^{2}}\] Area of sector centred at                         \[B=\frac{\angle B}{{{360}^{o}}}\times \pi {{(7)}^{2}}c{{m}^{2}}\] Area of sector centred at                         \[C=\frac{\angle C}{{{360}^{o}}}\times \pi {{(7)}^{2}}c{{m}^{2}}\] Total Area of all the three sectors      \[=\pi \frac{{{(7)}^{2}}}{{{360}^{o}}}(\angle A+\angle B+\angle C)\] \[=\frac{22}{7}\times \frac{7\times 7}{{{360}^{o}}}\times 180=77c{{m}^{2}}\]            Area of shaded region                        = Area of \[\Delta ABC-\] - Area of three sectors        \[=(168-77)c{{m}^{2}}=91c{{m}^{2}}\] 


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