The sum of the radius and the height of a cylinder is 19 m. The total surface area of the cylinder is 1672 m², what is the volume of the cylinder ?
a) 3080 m³
b) 2940 m³
c) 3220 m³
d) 2660 m³

Answer: a
Explanation: Let the radius of the cylinder be r and height be h
Then, r + h = 19
Again, total surface area of cylinder = $$\left( {2\pi rh + 2\pi {r^2}} \right)$$
$$\eqalign{ & 2\pi r\left( {h + r} \right) = 1672 \cr & 2\pi r \times 19 = 1672 \cr & 38\pi r = 1672 \cr & \pi r = \frac{{1672}}{{38}} = 44\,m \cr & r = \frac{{44 \times 7}}{{22}} = 14\,m \cr} $$
Height = 19 – 14 = 5 m
Volume of cylinder :
$$\eqalign{ & = \pi {r^2}h \cr & = \frac{{22}}{7} \times 14 \times 14 \times 5 \cr & = 22 \times 2 \times 14 \times 5 \cr & = 3080\,{m^3} \cr} $$