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

  • question_answer
    Column-II give value of x and y for pair of equation given in Column-II.
    Column - I Column - II
    A. \[2x+y=8\], \[x+6y=15\] 1. (3, 4)
    B. \[5x+3y=35\], \[2x+4y=28\] 2. (4, 5)
    C. \[15x+4y=61\] \[4x+15y=72\] 3. (3, 2)

    A) A-R,     B-P,     C-Q

    B) A-P,     B-R,     C-Q

    C) A-R,     B-Q,    C-P

    D) None of these

    Correct Answer: C

    Solution :

    [A] Given,   \[2x+y=8\]               … (i)
    and      \[x+6y=15\]                       ... (ii)
    Multiplying Eq. (ii) by 2, we get
    \[2x+11y=30\]                              ... (iii)
    Subtracting Eq. (i) from Eq. (iii), we get
    \[11y=22\]
    \[\Rightarrow \,\,\,\,y=2\]
    From Eq. (i), we get
    \[2x+2=8\]
    \[\Rightarrow \,\,\,2x=6\]
    \[\Rightarrow \,\,\,x=3\]
    So, \[\left( x,y \right)=\left( 3,2 \right)\]
    [B] Given, 5x + 3y = 35                         ...(i)
    and    2x+4y=28                                   ...(ii)
    On dividing Eq. (ii) by 2, we get
    \[x+2y=14\]                                          ...(iii)
    On multiplying Eq. (iii) by 5, we get
    \[5x+10y=70\]                                      ...(iv)
    On subtracting Eq. (i) from Eq. (iv),
    we get
    7y=35
    \[\Rightarrow \,\,\,\,y=5\]
    From Eq. (iii), we get
    \[x+2\left( 5 \right)=14\]
    0\[\Rightarrow \,\,\,x+10=14\]
    \[\Rightarrow \,\,x\,=4\]
    So, \[\left( x,\,\,y \right)=\left( 4,\,\,5 \right)\]
    [C] Given,\[15x+4y=61\]                        ...(i)
    and    \[4x+15y=72\]                            ...(ii)
    On multiplying Eq. (i) by 4 and Eq. (ii)
    by 15, we get
    \[60x+16y=244\]                                 ...(iii)
    and \[60x+225y=1080\]          ...(iv)
    On subtracting Eq. (iii) from Eq. (iv),
    we get
    \[209y\text{ }=836\]
    \[\Rightarrow \,\,\,\,\,y=4\]
    From Eq. (i), we get
    \[15x\text{ }+4\text{ }\left( 4 \right)\text{ }=61\]
    \[\Rightarrow \,\,\,\,15x+16=61\]
    \[\Rightarrow \,\,\,\,15x=45\]
    \[\Rightarrow \,\,\,\,x=3\]
    So, \[\left( x,y \right)=\left( 3,4 \right)\]


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