Question

In what ratio is a line segment joining the points (-2,-3) and (3,7) divided by y axis?
$
  {\text{A}}{\text{. }}\dfrac{2}{3}{\text{ }} \\
  {\text{B}}{\text{. }}\dfrac{3}{2}{\text{ }} \\
  {\text{C}}{\text{. }}\dfrac{4}{5}{\text{ }} \\
  {\text{D}}{\text{. }}\dfrac{5}{4}{\text{ }} \\
 $

Answer 1

Hint:In this problem first we let the ratio in which $y$axis divides the given line segment be in $m:n$. Then we apply the Section Formula on coordinates of that point to get a relation between $m{\text{ and }}n$. And finally we put $x$ coordinate of points obtained from Section Formula to get a ratio of $m{\text{ and }}n$.

Complete step-by-step answer:
Let y axis divide the line segment joining the point (-2,-3) and (3,7) in m:n ratio internally.
Since, the line segment is divided by y axis so$x$ coordinate of the point is 0. Let the coordinates of the point which divides the line segment be (0,y) .
Section Formula: If a point divides a line segment in $m:n$ whose endpoints coordinates are $({x_1},{y_1}){\text{ and }}({x_2},{y_2})$ then the coordinates of that point are
$\Rightarrow \left( {\dfrac{{m{x_2} + n{x_1}}}{{m + n}},\dfrac{{m{y_2} + n{y_1}}}{{m + n}}} \right) \\$
Using Section Formula the coordinates of the point of division of the line segment whose endpoints (-2,-3) and (3,7) in m:n ratio.
$
   \Rightarrow \left( {\dfrac{{m(3) + n( - 2)}}{{m + n}},\dfrac{{m(7) + n( - 3)}}{{m + n}}} \right) \\
   \Rightarrow \left( {\dfrac{{3m - 2n}}{{m + n}},\dfrac{{7m - 3n}}{{m + n}}} \right){\text{ eq}}{\text{.1}} \\
$
Since we let the coordinates of division points be (0,y) .
Then,
$\Rightarrow \left( {\dfrac{{3m - 2n}}{{m + n}},\dfrac{{7m - 3n}}{{m + n}}} \right) = (0,y) \\$
On comparing $x - $coordinate of above equation we get
$
   \Rightarrow \dfrac{{3m - 2n}}{{m + n}} = 0 \\
   \Rightarrow 3m - 2n = 0 \\
   \Rightarrow 3m = 2n \\
   \Rightarrow \dfrac{m}{n} = \dfrac{2}{3} \\ $

Therefore, the ratio in which $y$-axis divides the given line segment is $2:3$.
Hence, option A. is correct

Note:Whenever you get this type of problem the key concept of solving is to have knowledge about
how a given point divides the line segment like in this question dividing point lies on y axis so its coordinates must be in the form$(0,y)$. And using Section Formula \[\left( {\dfrac{{m{x_2} + n{x_1}}}{{m + n}},\dfrac{{m{y_2} + n{y_1}}}{{m + n}}} \right)\] you can find the required result.