9th Class Mathematics Lines and Angles Question Bank Lines and Angles

  • question_answer
    In the given figure, find the value of x.

    A) \[{{30}^{o}}\]

    B) \[{{10}^{o}}\]

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

    D)        \[{{20}^{o}}\]

    Correct Answer: A

    Solution :

    As, \[EF||AB\]and FA is transversal \[\therefore \]\[\angle EFA=\angle FAB\]  (alternate interior angles) Also, \[CD||AB\]and CA is transversal \[\therefore \]\[\angle DCA+\angle BAC={{180}^{o}}\](co-interior angles) \[\Rightarrow \]\[{{145}^{o}}+\angle BAC={{180}^{o}}\Rightarrow \angle BAC={{35}^{o}}\] Now, \[\angle FAB=x+\angle CAB\]  \[\Rightarrow \]\[{{65}^{o}}=x+{{35}^{o}}\Rightarrow x={{30}^{o}}\]


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