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

  • question_answer
    In the given figure \[\mathbf{AB}\parallel \mathbf{CD}\parallel \mathbf{EF}\]. If \[\mathbf{5x}=\mathbf{4y}\] and \[\mathbf{z}=\mathbf{y}+\mathbf{10}\], then the value of w is

    A)  \[{{60}^{{}^\circ }}\]                       

    B)  \[{{50}^{{}^\circ }}\]

    C)  \[{{90}^{{}^\circ }}\]                                   

    D)  \[{{70}^{{}^\circ }}\]

    Correct Answer: D

    Solution :

    (d): Given \[5x=4y=a\Rightarrow x=\frac{\alpha }{5},y=\frac{\alpha }{4}\] \[\therefore \]\[AB\parallel CD\] \[\therefore \]\[a=x\] \[\therefore \]\[a+y={{180}^{{}^\circ }}\] \[\therefore \]\[\frac{\alpha }{5}+\frac{\alpha }{4}={{180}^{{}^\circ }}\] \[\therefore \]\[9\alpha =180\times 20\Rightarrow \alpha =400\] \[\therefore \] \[y=\frac{400}{4}={{100}^{{}^\circ }}\] \[\therefore \]\[z=y+10={{100}^{{}^\circ }}+{{10}^{{}^\circ }}={{110}^{{}^\circ }}\] and \[w+z={{180}^{{}^\circ }}\] (Linear pair) \[w+{{110}^{{}^\circ }}={{180}^{{}^\circ }}\] \[w={{70}^{{}^\circ }}\]


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