At what temperature, the rms velocity of gas shown at 50°C will be doubled

${\mathrm{C}}_{\mathrm{rms}}=\sqrt{\frac{3\mathrm{RT}}{\mathrm{M}}}$ Where T is in kelvin scale. For rms velocity to be doubled, T in kelvin scale must be raised 4 times. So it should be
$4\times (50+273)=1292\mathrm{K}=1292-273={1019}^{\circ }\mathrm{C}$.