The total surface area of a solid cylinder is $231 \mathrm{~cm}^{2}$ and its curved surface area is $\frac{2}{3}$ of the total surface area. Find the volume of the cylinder.
Curved surface area $=\frac{2}{3} \times$ total surface area $=\frac{2}{3} \times 231=2 \times 77=154 \mathrm{~cm}^{2}$
Now, total surface area - curved surface area $=2 \pi r h+2 \pi r^{2}-2 \pi r h$
Then $231-154=2 \pi r^{2}$
$\Rightarrow 2 \times \frac{22}{7} \times r^{2}=77$
$\Rightarrow r^{2}=\frac{77 \times 7}{44}=12.25$
$\Rightarrow r=3.5 \mathrm{~cm}$
Also, curved surface area $=154 \mathrm{~cm}^{2}$
$\Rightarrow 2 \pi r h=154$
$\Rightarrow 2 \times \frac{22}{7} \times 3.5 \times h=154$
$\Rightarrow h=\frac{154 \times 7}{44 \times 3.5}=7 \mathrm{~cm}$
$\therefore$ Volume of the cylinder $=\pi r^{2} h$
$=\frac{22}{7} \times(3.5)^{2} \times 7=269.5 \mathrm{~cm}^{3}$