Question

The diameter of the base of a right circular cylinder is $$42\ cm$$ and its height is $$10\ cm$$ . find the area of the curved surface and total surface area.

Answer 1

Diameter of the base of the cylinder $$= 42\ cm$$

$$ \therefore $$ r = radius of the base of the cylinder $$= 21\ cm$$

h $$=$$ height of the cylinder $$= 10\ cm$$

$$ \therefore $$ curved surface area of the cylinder = $$ 2 \pi rh $$

= $$ 2 \times \dfrac {22}{7} \times 10\ cm^2 $$

= $$ 2 \times 22 \times 3 \times 10\ cm^2 =1320\ cm^2 $$

total surface area of the cylinder = $$ 2 \pi r ( h+ r) $$

= $$2 \times \dfrac {22}{7} \times 21 \times (10 +21 )\ cm^2 $$

= $$ 2 \times 22 \times 3 \times 31 cm^2 = 4092\ cm^2 $$