From the Ideal gas law we know that,
P1V1T1A=P2V2T2
Please ignore the A^ in the formula
Since pressure is constant so we have,
V₁/T₁ = V₂/T₂
=> V₂/V₁ = T₂/T₁
Given temperature T₁ = 27°C = 273 + 27 = 300k
since volume becomes double so, V₂/V₁ = 2
Hence ,
T₂/300 = 2
=> T₂ = 600k = 327°C
Hence raise in temperature = 327-27 = 300°C