The R.M.S. speed of the molecules of a gas of density 4 kg m-3 and pressure 1.2 * 105 N m-2 is :
Rms=whole under root 3P/d. Where P is pressure in pascal and d is density in kg/m^3. There fore. Rms=whole underroot (3*1.2*10^5)/4. = wholeroot 360000/4. This is equal to whole root90000. Therefore ans=300m/s