1. The problem statement, all variables and given/known data an ideal gas is allowed to expand adiabatically until its volume increases by 50%. By what factor is the pressured reduced?(gamma=5/3) 2. Relevant equations P1V1^gamma=P2V2^gamma 3. The attempt at a solution P1V1^gamma=P2V2^gamma v2=v1+.5V1=3/2V1 (p1/P2)=(v2/v1)^gamma=(3/2v1/v1)^gamma=3/2^gamma so P2=P1/(3/2)^gamma=0.51P1 sp P2=.5P1 so reduced by approximately factor of 2 This is actually the correct answer, but i dont understand the why the intial setup of the calculation, is P1/P2=(V2/V1)^gamma, the problem is looking for the reduction of the pressure, could someone explain why your suppose to set up calculation this way?