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

  • question_answer
    The area of a rhombus is \[28\text{ }c{{m}^{2}}\]and one of its diagonals is 4 cm. What is its perimeter?

    A) \[4\sqrt{53}\,cm\]                      

    B) \[36\,cm\]         

    C)   \[2\sqrt{53}\,cm\]          

    D)    52 cm             

    Correct Answer: A

    Solution :

    Let \[AC=x\,cm\]and \[BD=4\,cm\](Given) Given area of ABCD \[ABCD=28\,c{{m}^{2}}\] \[\Rightarrow \]\[\frac{1}{2}\times x\times 4=28\Rightarrow x=14\,cm\] Clearly, \[AO=\frac{14}{2}=7cm.\] By Pythagoras? theorem, \[A{{O}^{2}}+B{{O}^{2}}=A{{B}^{2}}\] or \[{{7}^{2}}+{{2}^{2}}=53\]or \[AB=\sqrt{53}\] \[\therefore \]Perimeter \[=4AB=4\sqrt{53}\]


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