Find the ratio in which the line segment joining the points A(3,8) and B(-9, 3) is divided by the Y- axis.

Suppose, P be the point on Y axis divides segment AB in the ratio m:n.
Since P lies on Y axis, its x co-oordinate is zero.
Let P = (0,y)
By Section formula, x = (mx₂+nx₁)/(m+n)
Given A(x₁,y₁) = (3,8)
B(x₂,y₂) = (-9,3)
0 = m×-9+n×3/(m+n)
0 = (-9m+3n)/(m+n)
-9m+3n = 0
-9m = -3n
m/n = 3/9 = 1/3
The required ratio m:n = 1:3.