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

  • question_answer
    AB and CD are two parallel lines. The points B and C are joined such that\[\angle \mathbf{ABC}=\mathbf{6}{{\mathbf{0}}^{{}^\circ }}\]. A line CE is drawn making angle of \[\mathbf{40}{}^\circ \] with the line CB, EF is drawn parallel to AB. As show in figure then \[\angle \mathbf{CEF}\] is equal to:

    A)  \[{{160}^{{}^\circ }}\]      

    B)  \[{{150}^{{}^\circ }}\]

    C)  \[{{120}^{{}^\circ }}\]                                  

    D)  \[{{135}^{{}^\circ }}\]

    Correct Answer: A

    Solution :

    (a): \[\angle ABC=\angle BCD\text{ }as\text{ }AB\parallel CD\] \[\angle BCD={{60}^{{}^\circ }}\] \[\angle ECD={{60}^{{}^\circ }}-\angle BCE\] \[={{60}^{{}^\circ }}-{{40}^{{}^\circ }}={{20}^{{}^\circ }}\] \[\angle CEF+\angle ECD={{180}^{^{{}^\circ }}}\] \[\angle CEF={{180}^{{}^\circ }}-\text{ }{{20}^{{}^\circ }}={{160}^{{}^\circ }}\]                       


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