I was working on a problem that stated an airplane is flying at an altitude of 10km. In its nonpressureized cargo bay is a container of mercury 325 mm deep.(the container is vented to the local atmosphere) The first part just asked for the atmospheric pressure at 10km. Which I found in a table to be 26.5 kPa. But for the second part it asks to find the absolute pressure at 10km using the the 26.5 kPa and the height of the mercury column. My question is how does the mercury column help you with finding the absolute pressure when the problem just says the mercry is sitting in a container? Do I just use ro*g*h to find the pressure exerted on the mercury? I would think there would need to be a height difference in the mercury because of the pressure acting on it.