10th Class Mathematics Mensuration Question Bank Mensuration

  • question_answer
    If each side of an equilateral triangle be increased by 2 cm, its area is increased by\[2\sqrt{3}\]sq. cm. The length of each side of the original triangle is

    A)  1cm                 

    B)         \[\sqrt{3}\]

    C)  3 cm                     

    D)  \[\sqrt{3}+2\,cm\]

    Correct Answer: A

    Solution :

     If x is the side of an equilateral triangle, then its area \[{{A}_{1}}=\frac{{{x}^{2}}\sqrt{3}}{4}\] If each side is increased by 2, then area of the triangle                 \[{{A}_{2}}=\frac{{{(c+2)}^{2}}\sqrt{3}}{4}\] But         \[{{A}_{2}}={{A}_{1}}+2\sqrt{3}\] therefore \[\frac{{{(x+2)}^{2}}\sqrt{3}}{4}=\frac{{{x}^{2}}\sqrt{3}}{4}+2\sqrt{3}\] or        \[4x+4=8\] or         \[x=1\,cm\]          


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