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9th Class Mathematics Geometry Question Bank Geometry

  • question_answer
    In the given figure, \[\angle CAB\,\,=\,\,80{}^\circ \,,\angle ABC\,\,=\,\,40{}^\circ .\] The sum of \[\angle DAB\,+\,\,\angle ABD\] is equal to

    A) \[80{}^\circ \]

    B) \[100{}^\circ \]

    C) \[120{}^\circ \]  

    D) \[140{}^\circ \]

    Correct Answer: C

    Solution :

     From \[\Delta \,CAB,\] \[\angle C={{180}^{o}}-({{80}^{o}}+{{40}^{o}})={{60}^{o}}\] \[\therefore \]  \[\angle D={{60}^{o}}\] Thus, from \[\Delta \,DAB,\] \[\angle DAB+ABD={{180}^{o}}-\angle D\]                 \[={{180}^{o}}-{{60}^{o}}={{120}^{o}}\]


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