Question

Find the total surface area of a cone, if its slant height is 21 m and diameter of its base is 24 m.

Answer 1

Total surface area of the cone $= \pi rl + \pi r^2 = \pi r (l + r )$
Diameter, d = 24m
Radius, r = $\frac{24}{2}$ m = 12m
Slant height, l = 21 m
Total surface area of the cone = $\pi r (l + r )$
= $\frac{22}{7}$× 12 m × (12 m + 21 m)

= $\frac{22}{7}$ × 12 m × 33 m

= $\frac{8712}{7}$m²
= 1244.57 m²

Thus, total surface area of the cone = 1244.57 m².