Question:
In what ratio does the y-axis divide the join of P(−4, 2) and Q(8, 3)?
(a) 3 : 1
(b) 1 : 3
(c) 2 : 1
(d) 1 : 2
Solution:
(d) 1 : 2
Let $A B$ be divided by the $y$ axis in the ratio $k: 1$ at the point $P$.
Then, by section formula, the coordinates of P are
$P\left(\frac{8 k-4}{k+1}, \frac{3 k+2}{k+1}\right)$
But, P lies on the y axis; so, its abscissa is 0
$\Rightarrow \frac{8 k-4}{k+1}=0$
$\Rightarrow 8 k-4=0$
$\Rightarrow 8 k=4$
$\Rightarrow k=\frac{1}{2}$
Hence, the required ratio is $\frac{1}{2}: 1$, which is same as $1: 2$.