To solve this problem use π=22/7
Problem from RS Aggarwal book, problem number 20, page number 824, exercise 17C, chapter volume and surface area of solid.
Chapter Mensuration
Deepak BoraNewbie
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, then find the area of material used for making it.
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solution
given data
Radius of open side, R=10 cm
Radius of upper base, r=4 cm
Slant height, l=15 cm
The area of material used=π[R+r]l+πr²
= [22/7] × [10+4] × 15 + [ [22/7] × 4 × 4
=[22/7] ×14×15 + [[22/7]×4×4]
= [22/7]×210+16
= [22/7] × 226
= 4972/7 cm²
= 710.28 cm²
∴ the area of material used for making the fez is 710.28 cm²