1. The problem statement, all variables and given/known data There are two similar atmosphere ISA +30C and ISA tropical Maximum, they have identical: Mean Sea level conditions, same basic shape of temperature profile and same lapse rate in troposphere. The difference is the altitude of the tropopause and hence a different temperature in the stratosphere if that temperature in the tropical maximum is -30C find the difference in pressure between the two conditions at an altitude of 16,000 m. 2. Relevant equations 3. The attempt at a solution So the tropopause is at an alitutde of 11km for ISA + 30C and 11.54km for tropical maximum after which the atmosphere is isothermal. So i can do the question now with resource of an ISA chart available where i can find the appropriate density for the altitude however we dont get an ISA chart in the exam and since the density lapse rate isnt a uniform one how would i know the value of the density to use or is there another method to find the pressure?