11th Class Mathematics Sample Paper Mathematics Olympiad - Sample Paper-7

  • question_answer
    In what ratio, the line joining \[\left( -\mathbf{1},\mathbf{1} \right)\] and \[\left( \mathbf{5},\mathbf{7} \right)\] is divided by the line \[\mathbf{x}+\mathbf{y}=\mathbf{4}?\]

    A)  \[2:1\]                          

    B)  \[1:2\]          

    C)  \[2:3\]                          

    D)  \[3:2\]

    Correct Answer: B

    Solution :

    [b] Let p be a point on the line\[x+y=4\], which divide the line joining \[A\left( -1,1 \right)\]and\[B\left( 5,7 \right)\]. P divide the line joining A and B be \[\lambda :1\] \[\therefore P\equiv \left( \frac{5\lambda +(-1)}{\lambda +1}.\frac{7\lambda +1}{\lambda +1} \right)\] Now, \[x+y=4\] \[\therefore \frac{5\lambda -1}{\lambda +1}=\frac{7\lambda +1}{\lambda +1}=4\] \[\Rightarrow 5\lambda +7\lambda -1+1=4\left( \lambda +1 \right)\] \[8\lambda =4\] \[\lambda =\frac{1}{2}=1:2\] Hence, option [b] is correct.


You need to login to perform this action.
You will be redirected in 3 sec spinner