Question

Surface area of a cone is 188.4 sq.cm and its slant height is 10 cm. Find its perpendicular height (π = 3.14).

Answer 1

Given: Length (l) =10 cm, curved surface area of the cone = 188.4 sq.cm 

To find: Perpendicular height (h) of the cone

i. Curved surface area of the cone = πrl 

∴ 188.4 = 3.14 x r x 10

ii. Now, l² = r² + h² 

∴ 10² = 6² + h² 

∴ 100 = 36 + h² 

∴ 100 – 36 = h² 

∴ h² = 64 

∴ h = √64 … [Taking square root on both sides] 

= 8 cm 

∴ The perpendicular height of the cone is 8 cm.