Answer :
[tex]\begin{gathered} \text{Given} \\ r=8\text{ cm} \\ h=3r=3(8\text{ cm})=24\text{ cm} \end{gathered}[/tex]
Recall that the surface area of the cylinder is
[tex]\begin{gathered} SA=2\pi rh+2\pi r^2 \\ \text{where} \\ r\text{ is the radius} \\ h\text{ is the height} \end{gathered}[/tex]Given the following
radius of 8 cm, and height of 24 cm (3 times the radius), then the surface area of the cylinder is
[tex]\begin{gathered} SA=2\pi rh+2\pi r^2 \\ SA=2\pi(8\text{ cm})(24\text{ cm})+2\pi(8\text{ cm})^2 \\ SA=384\pi\text{ cm}^2+128\pi\text{ cm}^2 \\ SA=512\pi\text{ cm}^2 \\ \; \\ \text{Therefore, the surface area of the cylinder is }512\pi\text{ cm}^2 \end{gathered}[/tex]