9th Class Mathematics Heron's Formula Question Bank Herons Formula

  • question_answer
    The perimeter of a field in the form of an equilateral triangle is 36 cm, then its area is given by

    A) \[98\sqrt{3}\,c{{m}^{2}}\]                   

    B)        \[8\sqrt{3}\,c{{m}^{2}}\]                    

    C)        \[42\sqrt{3}\,c{{m}^{2}}\]                   

    D)         \[36\sqrt{3}\,c{{m}^{2}}\]      

    Correct Answer: D

    Solution :

    Since. All the sides are equal in an equilateral triangle. So, perimeter = a + a + a, where a is the side of equilateral triangle. \[\Rightarrow \]\[3a=36\Rightarrow a=12\,cm\] Area \[=\frac{\sqrt{3}}{4}{{a}^{2}}=\frac{\sqrt{3}}{4}{{(12)}^{2}}=\frac{\sqrt{3}}{4}\times 44\] \[=36\sqrt{3}\,c{{m}^{2}}\]


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