BCECE Engineering BCECE Engineering Solved Paper-2014

  • question_answer
    The equation of the plane meets the axes in A, and C such that the centroid of the \[\Delta \]ABC is\[\left( \frac{1}{3},\frac{1}{3},\frac{1}{3} \right),\] is given by

    A) \[x+y+z=1\]                       

    B) \[x+y+z=2\]

    C) \[\frac{x}{3}+\frac{y}{3}+\frac{z}{3}=3\]               

    D) \[x+y+z=\frac{1}{3}\]

    Correct Answer: A

    Solution :

    Let the equation of plane be     \[\frac{x}{a}+\frac{y}{b}+\frac{z}{c}=1\]                                                 ? (i) Since, the plane meet the coordinate axes at A B and C. \[\therefore \]The coordinates of these points are \[A(a,0,0),B(0,b,0)\] and \[C(0,0,c),\] respectively. Then, centroid of \[\Delta ABC\]is\[\left( \frac{a}{3},\frac{b}{3},\frac{c}{3} \right),\] but it is given \[\left( \frac{1}{3},\frac{1}{3},\frac{1}{3} \right)\] \[\therefore \]  \[\frac{a}{3}=\frac{1}{3},\frac{b}{3}=\frac{1}{3},\frac{c}{3}=\frac{1}{3}\] \[\Rightarrow \]               \[a=1,b=1,c=1\] On putting the value of a, b and c in Eq. (i). we get \[\frac{x}{y}+\frac{y}{1}+\frac{z}{1}=1\Rightarrow x+y+z=1\]


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