Question

A cylinder has a radius of 7 inches and a height of 20 inches. Which is closest to the surface area

of this cylinder?

517 sq in
769 sq in
1,187 sq in
3,077 sq in
​

Answer 1

`\bf \stackrel{\textit{surface area of a right-circular cylinder}}{SA=2\pi r(h+r)~~ \begin{cases} r=radius\\ h=height\\[-0.5em] \hrulefill\\ r=7\\ h=20 \end{cases}}\implies SA=2\pi (7)(20+7) \\\\\\ SA=14\pi (27)\implies SA=378\pi \implies \boxed{SA\approx 1187.52}`

which one is closest from that list? well, pretty sure you already know.

Answer 2

The surface area of a cylinder with a height of 20 in and a 7 in radius is 1,187.52 which is closest to C) 1,187 sq in