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  3. CEE Kerala Engineering

CEE Kerala Engineering CEE Kerala Engineering Solved Paper-2011

  • question_answer
    If\[a=2i-7j+k\]and\[b=i+3j-5k\]and \[a.mb=120,\]then the value of m is equal to

    A)  5                                            

    B)  \[-24\] 

    C)  \[-5\]                                   

    D)         \[120\]

    E)  \[24\]

    Correct Answer: C

    Solution :

    Given,\[a=2i-7j+k,\text{ }b=i+3j-5k\] and \[a.mb=120\] \[\Rightarrow \]\[(2i-7j+k).(mi+3mj-5mk)=120\] \[\Rightarrow \]\[2m-21m-5m=120\] \[\Rightarrow \]\[-24m=120\] \[\Rightarrow \] \[m=-5\]


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