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AMU Medical AMU Solved Paper-1995

  • question_answer
    Two vectors \[\overrightarrow{A}=4\hat{i}+5\hat{j}+r\hat{k}\] and\[\overrightarrow{B}=2\hat{i}-4\hat{j}+6\hat{k}\] are perpendicular to each other if the scalar r is

    A)  4                 

    B)  2

    C)  0                 

    D)  \[-2\]

    Correct Answer: B

    Solution :

    :\[\overrightarrow{A}\,\overrightarrow{B}=0\]if\[\overrightarrow{A}\]and\[\overrightarrow{B}\]are perpendicular to each other. \[\therefore \] \[(4\hat{i}+5\hat{j}+r\hat{k}).(2\hat{i}-4\hat{j}+6\hat{k})=0\] \[\therefore \] \[8-20+6r=0\] or \[6r=12\]         or \[r=2\]


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