Correct answer: V2 = 200 × √(2)
The R.M.S. velocity of gas molecules is proportional to the square root of the absolute temperature. Converting temperatures to Kelvin, T1 = 300 K and T2 = 400 K. Using the relation V2 = V1 × √(T2/T1), we get V2 = 200 × √(400/300) = 200 × √(4/3) = 200 × √(2).