To solve this question we will use the following formula for the volume of a cone:
[tex]\begin{gathered} V=\frac{1}{3}\pi r^2h, \\ \text{where r is the radius of the cone and h is its height.} \end{gathered}[/tex]Substituting
[tex]\begin{gathered} r=\frac{9m}{2}=4.5m, \\ h=4m, \end{gathered}[/tex]we get:
[tex]\begin{gathered} V=\frac{1}{3}\pi(4.5m)^2\cdot4m \\ =\frac{1}{3}\pi(20.25m^3)\cdot4m \\ =27\pi m^3 \\ \approx84.8m^3. \end{gathered}[/tex]Answer:
[tex]84.8m^3.[/tex]