Before anything, my apologies for offering such an elementary question about gas pressure. Any help would be appreciated. 1. The problem statement, all variables and given/known data There are two chambers. One is 100 L, containing air at a pressure of 200 kPa. The other, joined to it, is 10 L and contains air at a pressure of 20 kPa. The airtight seal between the chambers is broken. What is the final, stable pressure of the combined chambers? 2. Relevant equations Basic arithmetic. 3. The attempt at a solution I've assumed that it's the greater pressure (200 kPa) that matters, not the lesser. (That is, the pressures aren't additive.) So I get 100 L / 110 L = 0.909. Then: 0.909 * 200 kPa = 181.818 kPa for the whole, combined system. I suspect that I'm wrong, but I don't know how or why. Anyone care to put me on the right path?