Railways Sample Paper RRB (Group D) Sample Test Paper-14

  • question_answer
    The area of the triangle formed by the lines \[5x+7y=35,\,4x+3y=\text{ }12and\text{ }x-axis\text{ }is\]

    A)  \[\frac{160}{13}sq.unit\]                       

    B)  \[\frac{150}{13}sq.unit\]

    C)  \[\frac{140}{13}sq.unit\]           

    D)  \[10\,sq.unit\]

    Correct Answer: A

    Solution :

    [a] \[5x+7y=35\,\,\,\,\,\,\,\,\,\,\,\,\,\,...(i)\]              ? (i) \[4x+3y=12\,\,\,\,\,\,\,\,\,\,\,\,\,\,...(ii)\]                  ? (ii) By equation \[(i)\times 4\text{ }-(ii)\times 5\] \[\begin{matrix}    20x & + & 28y & = & 140  \\    20x & + & 15y & = & 60  \\    - & {} & - & {} & -  \\    {} & {} & 13y & = & 80  \\ \end{matrix}\] \[\Rightarrow \,\,y=\frac{80}{13}\]=Height of triangle Point of intersection on x-axis of equation \[5x+7y=35\] \[\Rightarrow 5x+7\times 0=35\] \[\Rightarrow 5x=35\] \[\Rightarrow x=7\] \[\therefore \,\,\,(7,\,0)\] Similarly, point of intersection of \[4x+3y=12=(3,\,\,0)\] \[\therefore \,\,\,Base=7-\,3=4\] \[\therefore Area=\frac{1}{2}\times 4\times \frac{80}{13}=\frac{160}{13}\,\,sq.unit\]


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