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.