Initial pressure P1 = P
Final pressure P2 = P + \(\frac{0.4P}{100}\)
T1 = T, T2 = T + 1
At constant volume \(\frac{P_2}{P_1}\) = \(\frac{T_2}{T_1}\)
\(\frac{P(1+ 0.004)}{P}\) = \(\frac{T - 1}{T}\)
PT + 0.004 PT = PT + P
0.004PT = P
∴ T = \(\frac{1}{0.004}\)
= 250 K
∴ Initial Temperature of the gas = 250 K