The average speed of an ideal gas molecules at 27°C is 0.3 ms^-1. The average speed at 927°C will be in m/sec is:

The expression of average speed is ${\mathrm{c}}_{\mathrm{av}}=\sqrt{8\mathrm{RT}/\mathrm{\pi M}}$. For two temperatures, we have

Expression of average speed is ${\mathrm{C}}_{\mathrm{average} \mathrm{speed}}=\sqrt{\frac{8\mathrm{RT}}{\mathrm{\pi M}}}$. From there, 

$\frac{{\mathrm{C}}_{\mathrm{average} \mathrm{speed}-2}}{{\mathrm{C}}_{\mathrm{average} \mathrm{speed}-1}}=\frac{{\mathrm{T}}_2}{{\mathrm{T}}_1}$

T₂ is 927⁰C and T₁ is 27⁰C.

$\frac{{\mathrm{C}}_2}{{\mathrm{C}}_1}=\sqrt{\frac{927+273}{27+273}}=\sqrt{\frac{1200}{300}}=2$ ${\mathrm{c}}_2=2{\mathrm{c}}_1=2\left(0.3{\mathrm{ms}}^{-1}\right)=0.6{\mathrm{ms}}^{-1}$