Find

(i) the curved surface area.

(ii) the total surface area of a hemisphere of radius 21 cm.

(i) Given, radius = 21 cm.

Curved surface area of hemisphere = 2πr².

Putting values in equation we get,

$\text{Curved surface area of hemisphere } = 2 \times \dfrac{22}{7} \times (21)^2 \\[1em] = \dfrac{2 \times 22 \times 441}{7} \\[1em] = \dfrac{19404}{7} = 2772 \text{ cm}^2.$

Hence, the curved surface area of hemisphere = 2772 cm².

(ii) Total surface area of hemisphere = 3πr².

Putting values in equation we get,

Total surface area of hemisphere = 3 x $\dfrac{22}{7}$ x (21)²

$= \dfrac{3 \times 22 \times 441}{7} \\[1em] = \dfrac{29106}{7} = 4158 \text{ cm}^2.$

Hence, the total surface area of hemisphere = 4158 cm².