Answer:
V = 381.70 m³
Step-by-step explanation:
ρ air = 1.28 kg / m³
ρ helium = 0.18 kg / m³
R = 4.5 m
Vb = 0.068 m³
mb = 123 kg
To determine the volume of helium in the balloon when fully inflated
V = 4 / 3 π * R ³
V = 4 * π / 3 ( 4.5 m )³
V = 381.70 m³
To determine the mass total
m = ρ helium * V
m = 0.18 kg / m³ * 381.70 m³
m = 68.70 kg
mt = ( 68.70 + 123 )kg
mt = 191.70 kg