KVPY Sample Paper KVPY Stream-SX Model Paper-31

  • question_answer
    The perpendicular distance of point \[(2,-1,4)\] from the line \[\frac{x+3}{10}=\frac{y-2}{-7}=\frac{z}{1}\] lies between:

    A) \[(2,3)\]

    B) \[(3,4)\]

    C) \[(4,5)\]

    D) \[(1,2)\]

    Correct Answer: B

    Solution :

    Let the foot of perpendicular from \[P(2,-1,4)\] to the given line be\[A(10\lambda -3,-7\lambda +2,\lambda )\]
    \[\overrightarrow{PA.}(10i-7j+k)=0\]\[\Rightarrow \]\[10(10\lambda -5)-7(-7\lambda +3)+1(\lambda -4)=0\]\[\Rightarrow \]\[150\lambda =75\]\[\Rightarrow \]\[\lambda =\frac{1}{2}\]
    \[|\overrightarrow{PA}|=\sqrt{{{(10\lambda -5)}^{2}}+{{(-7\lambda +3)}^{2}}+{{(\lambda -4)}^{2}}}\]
    \[=\sqrt{0+{{\left( \frac{1}{2} \right)}^{2}}+{{\left( \frac{7}{2} \right)}^{2}}}=\sqrt{\frac{50}{4}}\]
    Which lies in\[(3,4).\]


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