Consider the sound wave travelling in ideal gases of \( \mathrm{He}, \mathrm{CH}_{4}, \) and \( \mathrm{CO}_{2} \). All the gases have the same ratio \( \frac{P}{\rho} \), where \( P \) is the pressure and \( \rho \) is the density. The ratio of the speed of sound through the gases \( v_{\mathrm{He}} : v_{\mathrm{CH}_{4}} : v_{\mathrm{CO}_{2}} \) is given by:
