An insulated container of gas has two chambers separated by an insulating partition. One of the chambers has volume ${V_1} and contains ideal gas at pressure {P_1} and temperature {T_1}. The other chamber has volume {V_2} and contains ideal gas at pressure {P_2} and temperature {T_2}$. If the partition is removed without doing any work on the gas, the final equilibrium temperature of the gas in the container will be