A large weather balloon contains 365m^3 of helium at 15 C and 80.0 kPa. As the balloon rises into the atmosphere , what volume will it occupy at 60.0 kPa and -20.0 C if the amount remains constant?
the volume is inversely proportional to the ambient pressure
and directly proportional to the ambient absolute (Kelvin) temperature
v = 365 * (80.0 / 60.0) * [(273 - 20.0) / (273 + 15)]