From the figure, find the ratio in which the line segment joining the points B(6, 7) and D(6, 1) is divided by y = 4.
Let P(x,4) divide AB in the ratio k:1.
By section formula, the coordinates of P are given by: (6k+6k+1,k+7k+1)
But P(x,4)=(6k+6k+1,k+7k+1) ⇒k+7k+1=4
⇒k+7 = 4k+4
⇒3k = 3
⇒k = 11
i.e., the line y = 4 divides AB in the ratio 1:1.