The lateral surface area of a cylinder
[tex]\begin{gathered} =2\pi rh \\ \text{from the given question radius =7ft and height= 21ft} \\ \pi=\text{ }\frac{22}{7} \\ \text{The lateral surface area of a cylinder =2}\times\frac{22}{7}\times7\times21 \\ \text{The lateral surface area of a cylinder =923.63ft}^2 \end{gathered}[/tex]