J & K CET Engineering J and K - CET Engineering Solved Paper-2007

  • question_answer
    Two vectors are given by \[\vec{A}=3\hat{i}+\hat{j}+3\hat{k}\]and \[\vec{B}=3\hat{i}+5\hat{j}-2\hat{k}\]. Find the third vector \[\vec{C},\] if \[\vec{A}+3\vec{B}-\vec{C}=\vec{0}\].

    A)   \[12\hat{i}+14\hat{j}+12\hat{k}\]

    B)  \[13\hat{i}+17\hat{j}+12\hat{k}\]

    C)  \[12\hat{i}+16\hat{j}-3\hat{k}\]

    D)  \[15\hat{i}+13\hat{j}+4\hat{k}\]

    Correct Answer: C

    Solution :

    Given,     \[\vec{A}=3\hat{i}+\hat{j}+3\hat{k}\] \[\vec{B}=3\hat{i}+5\hat{j}-2\hat{k}\] Here, \[\vec{A}+3\vec{B}=\vec{C}\] \[(3\hat{i}+\hat{j}+3\hat{k})+3(3\hat{i}+5\hat{j}-2\hat{k})=\vec{C}\] \[\Rightarrow \] \[\vec{C}=12\hat{i}+16\hat{j}-3\hat{k}\]


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