Answer :

Given:

[tex]\text{diameter(d)}=18\text{ cm ; height(h)=20 cm}[/tex][tex]\begin{gathered} r=\frac{18}{2} \\ r=9\operatorname{cm} \end{gathered}[/tex][tex]\begin{gathered} \text{Volume of soil should he buy to fill the planter=Volume of a cylinder} \\ \text{Volume of soil should he buy to fill the planter=}\pi(r^2)h \\ \text{Volume of soil should he buy to fill the planter=}3.14(9^2)20 \\ \text{Volume of soil should he buy to fill the planter=}5086.8cm^3 \end{gathered}[/tex]