This is the important problem, in this problem use π = 3.14, Problem from RS Aggarwal book, Problem number 2, chapter volume and surface area of solid, Exercise 17 c
Deepak BoraNewbie
The radii of the circular ends of a solid frustum of a cone are 18 cm and 12 cm and its height is 8 cm. Find its total surface area.
Share
solution
given data
Height = 8 cm
Base radii, R= 18 cm and r = 12 cm
the slant height
l = √[(R -r)² + h²]
= √[(18-12 )² + 8²]
= √ 6² +8²
= √36 + 64
= √100
l = 10 cm
Total surface area of the solid frustum = π(R+r)l +πR² +πr²
= 3.14 × ( 18 + 12 ) ×10 + [3.14 ×18²]+[ 3.14 ×12²]
= 3.14 × ( 300 + 324 + 144 )
= 3.14 × 768
= 2411.52 cm²