A man is walking on a straight line. The arithmetic mean of the reciprocals of the intercepts of this line on the coordinate axes
Question:
A man is walking on a straight line. The arithmetic mean of the reciprocals of the intercepts of this line on the coordinate axes
is $\frac{1}{4} .$ Three stones A, B and C are placed at the
points $(1,1),(2,2)$ and $(4,4)$ respectively. Then which of these stones is / are on the path of the man?
Correct Option: , 4
Solution:
Let the line be $y=m x+c$
$\mathrm{x}$-intercept : $-\frac{\mathrm{c}}{\mathrm{m}}$
y-intercept : c
A.M of reciprocals of the intercepts :
$\frac{-\frac{\mathrm{m}}{\mathrm{c}}+\frac{1}{\mathrm{c}}}{2}=\frac{1}{4} \Rightarrow 2(1-\mathrm{m})=\mathrm{c}$
line $: y=m x+2(1-m)=c$
$\Rightarrow \quad(\mathrm{y}-2)-\mathrm{m}(\mathrm{x}-2)=0$
$\Rightarrow$ line always passes through $(2,2)$
Ans. 4