7th Class Mathematics The Triangle and its Properties Question Bank The Triangle and Its Properties

  • question_answer
    In the figure, not drawn to scale, ACDF is a rectangle and BDE is a triangle. Find \[\angle BED\]

    A)  \[{{42}^{o}}\]                    

    B)  \[{{52}^{o}}\]              

    C)         \[{{128}^{o}}\]          

    D)         \[{{134}^{o}}\]                  

    Correct Answer: B

    Solution :

    \[\angle CDB+\angle BDE={{90}^{o}}\]  (Angle of a rectangle) \[\Rightarrow \]   \[{{48}^{o}}+\angle BDE={{90}^{o}}\] \[\Rightarrow \]    \[\angle BDE={{90}^{o}}-{{48}^{o}}={{42}^{o}}\] In \[\Delta BED\] \[\angle EBD+\angle BDE+\angle BED={{180}^{o}}\]                         (Angle sum property) \[\Rightarrow \] \[{{86}^{o}}+{{42}^{o}}+\angle BED={{180}^{o}}\] \[\Rightarrow \] \[\angle BED={{180}^{o}}-({{86}^{o}}+{{42}^{o}})={{52}^{o}}\]


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