Answer:
[tex]V=16.65 m^3[/tex]
Explanation:
The volume of the balloon can be find compared the force in each cases so:
reduce 25% from 74kg
[tex]R=\frac{25}{100}*74kg=18.5kg[/tex]
So the net force uproad on the balloon is
[tex]F_b=18.5kg*g[/tex]
Now the density of the both gases air and helium are different however the volume is the same change offcorss the mass so:
[tex]P_h=\frac{m}{V}=0.179 kg/m^3[/tex]
[tex]P_A=1.29 kg/m^3[/tex]
[tex]F_b=F_A-F_H[/tex]
[tex]F_b=m_a*g-m_h*g[/tex]
[tex]m=P/V[/tex]
[tex]18.5kg*g=(1.29kg/m^3-0.179kg/m^3*)V*g[/tex]
[tex]V=\frac{18.5kg}{(1.29-0.179)kg/m^3}[/tex]
[tex]V=16.65 m^3[/tex]