The Total solution for NCERT class 6-12
A fez, the cap usedby the Turks, is shaped like the frustum of a cone (see Fig.). If its radius onthe open side is 10 cm, radius at the upper base is 4 cm and its slant heightis 15 cm, find the area of material used for making it.
Solution:
Given,
For the lower circular end, radius (r1)= 10 cm
For the upper circular end, radius (r2)= 4 cm
Slant height (l) of frustum = 15 cm
Now,
The area of material to be used for making thefez = CSA of frustum + Area of upper circular end
CSA of frustum = π(r1+r2)×l
= 210π
And, Area of upper circular end = πr22
= 16π
∴ The area of material used = 710 × (2/7) cm2