[tex]The\ volume\ of\ the\ sphere:V=\frac{4}{3}\pi R^3\\\\diameter=18in;\ the\ diameter=2\ times\ radius\ therefore\\ R=18in:2=9in\\\\so\\\\V=\frac{4}{3}\pi\cdot9^3=\frac{4}{3}\pi\cdot729=4\pi\cdot243=\boxed{972\pi\ (in^3)}\\\\approximate\ \pi\approx3.14,\ you\ have\ answer:\\\\V\approx972\cdot3.14=\boxed{3052.08\ (in^3)}[/tex]