Answer:
Option C
Explanation:
Plan This problem can be solved by using the concept of Graham's law of diffusion according to which rate of diffusion of non-reactive gases under similar conditions of temperature and pressure are inversely proportional to square root of their density
Rate of diffusion $\propto$ $\frac{1}{\sqrt{molar weight of gas}}$
Let distance covered by X is d, then distance covered by Y is 24-d
If rx and ry are the rate of diffusion of gases X and Y.
$\frac{r_{x}}{r_{y}}=\frac{d}{24-d}=\sqrt{\frac{40}{10}}=2$
d=48-2d
3d=48= d=16 cm
Hence,(c) is the correct choice