Im tryng to solve an equation for how pressure changes over time in a container. It goes something like this There is a 10 liter sealed container(V1) with x amount of initial pressure (P1), and a 1 liter container attached to it (V2) with one valve that opens between them, and then another valve that opens to atmosphere. The initial pressure in the 1 liter attachment is atmospheric (P2). For each cycle the valve opens between the pressureised 10 liter container and the one liter at 1 atm, the pressure then equalizes in both containers. Then the inner valve is closed and the outer valve is opened on the 1 liter container and pressure is vented to atmosphere (so the 1 liter container returns to 1atm) then the outside valve is closed and the cycle continues. I need to find out after how many cycles does the large 10 liter container reach a certain pressure above 1 atm... I can figure out what the pressure is in the container after they equalize each time which is P= (P1*V1 +P2*V2)/(V1+V2) So lets say the initial pressure is of P1 is 2atm after the first cycle the pressure would be P = (2*10l +1l*1atm)/(1l+10l) = 1.91 atm then the second cycle would be P = (1.91*10l +1l*1atm)/(1l+10l) = 1.83 atm etc etc so what would be the equation t describe this pressure drop over a certain number of cycles? i.e. P(c) = ?