Equal masses of ${\mathrm{H}}_2$, ${\mathrm{O}}_2$ and methane have been taken in a container of volume V at temperature 27°C in identical conditions. The ratio of the volumes of gases ${\mathrm{H}}_2$:${\mathrm{O}}_2$: methane would be

According to Avogadro's hypothesis, ratio of the volumes of gases will be equal to the ratio of their no. of moles. 

So, no. of moles= $\frac{\text{ Mass }}{\text{ Mol. mass }}$

$n_{{\mathrm{H}}_2}=\frac{w}{2};n_{{\mathrm{O}}_2}=\frac{w}{32};n_{{\mathrm{CH}}_4}=\frac{w}{16}$

$\text{ So, the ratio is }\frac{w}{2}:\frac{w}{32}:\frac{w}{16}\text{ or }16:1:2\text{ . }$