Question

Question 3
A fez, the cap used by the Turks, is shaped like the frustum of a cone. If its radius on the open side is 10 cm, radius at the upper base is 4 cm and its slant height is 15 cm, find the area of material used for making it.

Answer 1

R = 10 cm, r = 4 cm, slant height = 15 cm
Curved surface area of frustum
$=\pi (R+r)l$
$=\pi (10+4)15$
$=\frac{22}{7}\times 14\times 15=660c{m}^2$
Area of upper base
$=\pi r^2=\pi \times 4^2$
$=16\pi =50\frac{2}{7}c{m}^2$
Hence, total surface area
$=660+50\frac{2}{7}$
$=710\frac{2}{7}c{m}^2$