10th Class Mathematics Triangles Question Bank MCQs - Triangles

  • question_answer
     
    In the given figure\[DE||BC\]. If \[AD=x\]\[DB=x-2\], \[AE=x+2\] and \[EC=x-1\], then the value of x is

    A) 9

    B) 4

    C) 4.5

    D) 8

    Correct Answer: B

    Solution :

    Given in \[\Delta ABC\,DE\,|\,\,|\,\,BC\], Now, \[\frac{AD}{DB}=\frac{AE}{EC}\] [by Thales theorem] \[\Rightarrow \,\,\,\,\frac{x}{x-2}=\frac{x+2}{x-1}\] \[\Rightarrow \,\,\,x\left( x-1 \right)=\left( x-2 \right)\left( x+2 \right)\] \[\Rightarrow \,\,\,{{x}^{2}}-x={{x}^{2}}-4\] \[\therefore \,\,\,\,x=4\]


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