$30$ circular plates,each of radius $14\,cm$ and thickness $3\,cm$,are placed one above the other to form a cylindrical solid. Find:
$(i)$ the total surface area
$(ii)$ the volume of the cylinder so formed.

(N/A) Radius of one circular plate $(r)$ $= 14\,cm$.
Thickness of one circular plate $= 3\,cm$.
As the plates are placed one above the other,the height $(h)$ of the cylinder formed by $30$ plates $= 30 \times 3 = 90\,cm$.
$(i)$ Total surface area of the cylinder $= 2\pi r(r + h) = 2 \times \frac{22}{7} \times 14 \times (14 + 90) = 44 \times 2 \times 104 = 88 \times 104 = 9152\,cm^2$.
$(ii)$ Volume of the cylinder $= \pi r^2 h = \frac{22}{7} \times 14 \times 14 \times 90 = 22 \times 2 \times 14 \times 90 = 44 \times 1260 = 55440\,cm^3$.