We are given a balloon
and shape of balloon is always spherical
we have
diameter=18 inches
Let's assume radius of sphere as 'r'
so, we get
[tex]2r=18[/tex]
[tex]r=9[/tex]
now, we can use volume formula
[tex]V=\frac{4}{3} \pi r^3[/tex]
now, we can plug values
[tex]V=\frac{4}{3} \pi (9)^3[/tex]
[tex]V=4\cdot \:243\pi[/tex]
[tex]V=972\pi in^3[/tex].............Answer