To solve this we assume that the gas inside the
balloon is an ideal gas. Then, we can use the ideal gas equation which is
expressed as PV = nRT. At a constant temperature and number of moles of the gas
the product of PV is equal to some constant. At another set of condition of
temperature, the constant is still the same. Calculations are as follows:
P1V1 = P2V2
V2 = P1V1 / P2
V2 = 0.865 x 1.25 / 0.820
V2 = 1.32 L
