10th Class Mathematics Pair of Linear Equations in Two Variables Question Bank MCQs - Pair of Linear Equations in Two Variables

  • question_answer
    If the lines given by \[3x+2ky=2\]and \[2x+5y=1\] are parallel, then the value of k is

    A) \[-\frac{5}{4}\]

    B) \[\frac{2}{5}\]

    C) \[\frac{15}{4}\]

    D) \[\frac{3}{2}\]

    Correct Answer: C

    Solution :

    Condition for parallel lines is
    \[\frac{{{a}_{1}}}{{{a}_{2}}}=\frac{{{b}_{1}}}{{{b}_{2}}}\ne \frac{{{c}_{1}}}{{{c}_{2}}}\]            … (i)
    Given lines, \[3x+2ky-2=0\]
    and        \[2x+5y-1=0\]
    Here,       \[{{a}_{1}}=3,\,{{b}_{1}}=2k,\,{{c}_{1}}=-2\]
    and        \[{{a}_{2}}=2,\,{{b}_{2}}=5,\,{{c}_{2}}=-1\]
    From Eq. (i), \[\frac{3}{2}=\frac{2k}{5}\]
    \[\therefore \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,k=\frac{15}{4}\]


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