Two samples A and B of a gas initially at the same pressure and temperature are compressed from volume V to V/2 (A isothermally and B adiabatically). The final pressure of A is : 

less than the final pressure of B

For isothermally process :

\(P_1V = P'_2 \frac{V}{2}\)

\(\Rightarrow P'_2 = 2P_1\)

For adiabatic process :

\(P_1 V^{\gamma} = P_2 (\frac{V}{2})^{\gamma}\)

\(\Rightarrow P_2 = 2^{\gamma}P_1\)

Since, \(\gamma\) > 1, P₂ > P'₂