9th Class Mathematics Areas of Parallelograms and Triangles Question Bank Area of Parallelogram & Triangle

  • question_answer
    In the given figure, ABCD is a quadrilateral with AB parallel to DC and AD parallel to BC, ADC is a right angle. If the perimeter of the\[\Delta \mathbf{ABE}\]is 6 units, what is the of the quadrilateral?

    A)  \[2\sqrt{3}\]sq units  

    B)  4 sq units

    C)  3 sq units                   

    D)  \[4\sqrt{3}\]sq units

    Correct Answer: A

    Solution :

    (a): \[AB\parallel DC\] and \[AD\parallel BC\] In\[\Delta ABE\], \[\angle EAB=\angle ABE={{60}^{{}^\circ }}\] \[\Rightarrow \] \[\angle AE={{60}^{{}^\circ }}\] \[\Rightarrow \] \[\Delta ABE\] is an equilateral triangle. Now, Perimeter of \[\Delta ABE=6\] \[\Rightarrow \]\[AB+BE+EA=2\] And in \[\Delta ADE,\text{ }A{{E}^{2}}=A{{D}^{2}}+E{{D}^{2}}\] \[\Rightarrow \]\[4=A{{D}^{2}}+1\]       (Since. E is mid-point of CD) \[\Rightarrow \]\[AD=\sqrt{3}\]units Hence, area of quadrilateral \[ABCD=AB\times AD\] \[=2\times \sqrt{3}=2\sqrt{3}\]sq units      


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