volume of a gas is doubled when temperature raised from 0 C to 273 K. why?

The question has a mistake as 0°C is equal to 273 K. It should be :
“Volume of a gas is doubled when temperature raised from 0°C to 273°C. why?”

Let V be the volume of the gas at 0°C.

At O°C: V₁ = V, T₁ = (273 + 0) K = 273 K
At 273°C: V₂ = ?, T₂ = (273 + 273) K = 546 K

For a fixed amount of gas under constant pressure: V₁/T₁ = V₂/T₂
Then, V₂ = V₁ × (T₂/T₁)

Final volume, V₂ = V × (546/273) = 2V
Hence, Volume of the gas at 273°C = 2 × (Volume of the gas at 0°C)