Surface Area and Volume of a Cylinder

$V = \pi \times 9 \times 10 = 90\pi \approx 282.7 \text{ cm}^3$

$S = 2\pi \times 3 \times (3 + 10) = 6\pi \times 13 = 78\pi \approx 245.0 \text{ cm}^2$

A standard aluminium can has radius ≈ 3.3 cm and height ≈ 11.5 cm.

Volume: $V = \pi \times 3.3^2 \times 11.5 \approx \pi \times 10.89 \times 11.5 \approx 393 \text{ cm}^3$ — about 330 ml.

Surface area: $S = 2\pi \times 3.3 \times (3.3 + 11.5) \approx 2\pi \times 3.3 \times 14.8 \approx 307 \text{ cm}^2$ — the amount of aluminium sheet needed per can.

A farm water tank is 2 m in radius and 4 m tall. The owner wants to know how many litres it holds when full.

$V = \pi \times 4 \times 4 = 16\pi \approx 50.3 \text{ m}^3$

Since 1 m³ = 1,000 litres, the tank holds about 50,300 litres — enough to supply a household for weeks.

A concrete pillar has radius 0.4 m and height 3 m. The lateral surface area to be painted:

$S_{\text{lateral}} = 2\pi \times 0.4 \times 3 = 2.4\pi \approx 7.54 \text{ m}^2$

If one tin covers 5 m², the contractor needs 2 tins to coat the pillar.