9th Class Mathematics Triangles Question Bank Triangles

  • question_answer
    In the figure given, find\[\angle x\].

    A) \[{{40}^{o}}\]                        

    B)        \[{{110}^{o}}\]                      

    C)        \[{{45}^{o}}\]                        

    D)        \[{{65}^{o}}\]            

    Correct Answer: C

    Solution :

    From the figure, we have \[\angle ADB=\angle ABD.\](Since AB = AD.) \[\therefore \]\[\angle ADB={{180}^{o}}-{{110}^{o}}={{70}^{o}}\] But \[\angle ADB=\angle DAC+\angle ACD\] (Exterior angle of \[\Delta \Alpha DC.\]) \[\Rightarrow \]\[{{70}^{o}}={{x}^{o}}+{{25}^{o}}\] \[\Rightarrow \]\[{{x}^{o}}={{70}^{o}}-{{25}^{o}}={{45}^{o}}\]


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