Answer
See below
Work Step by Step
The surface area S and the volume V of a cylindrical can are given by $S=2\pi r^2+2\pi rh$ and $V=\pi r^2 h$
where $r$ is the radius and $h$ is the height.
An expression for the efficiency ratio is: $\frac{S}{V}=\frac{2\pi r^2+2\pi rh}{\pi r^2h}=\frac{\pi r(2r+2h)}{\pi r^2 h}=\frac{2(r+h)}{rh}$
