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JEE Main & Advanced JEE Main Paper (Held On 8 April 2017)

  • question_answer
    The area (in sq. units) of the parallelogram whooshed diagonals are along the vectors \[8\hat{i}-6\hat{j}\]and\[3\hat{i}+4\hat{j}-12\hat{k},\]is:  [JEE Online 08-04-2017]

    A)  20                                         

    B)  65

    C)  52                                         

    D)  26         

    Correct Answer: B

    Solution :

    \[{{d}_{1}}\times {{d}_{2}}=\left| \begin{matrix}    i & j & k  \\    8 & -6 & 0  \\    3 & 4 & -12  \\ \end{matrix} \right|\]\[=72\hat{i}-(-96)\hat{j}+50\hat{k}\]                 \[=5178+7056+2500\]                 \[|{{d}_{1}}\times {{d}_{2}}|=\sqrt{16900}=130\]                 \[A=\frac{1}{2}|{{d}_{1}}\times {{d}_{2}}|=\frac{1}{2}\times 130\]= 65


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