Gas M occupies a volume of 1000 c.c and contains X molecules. How many molecules will be present in gas N occupying a volume of 250 c.c?

$\dfrac{\text X}{4}$

Reason — Let molecules in gas N be Y.

$\dfrac{\text{Molecules in gas N}}{\text{Molecules in gas M}} = \dfrac{\text{Volume of gas N}}{\text{Volume of gas M}} \\[1em] \dfrac{\text{Y}}{\text{X}} = \dfrac{250}{1000} \\[1em] \text{Y} = \dfrac{250}{1000} \times \text{X} \\[1em] \text{Y} = \dfrac{\text{X}}{4}$

Hence, gas N contains $\dfrac{\text X}{4}$ molecules.