A card board tube is used to mail a poster. Tthe diameter of the tube is 72 cm and its length is 12cm. What is the surface area of the tube?

Answer 1

the circular side of the tube has surface area = Lpi(D) where L = length, D = diameter and pi = about 3.14

A = 72(3.14)(12) = 2712.96 cm^2

But you probably want to add the end area, at both ends. Their area = pi(r)^2 = pi(D/2)^2 = pi(72/2)^2 = pi(36)^2 = 3.14(1296) = 4069.44 cm^2

then multiply the end area by 2, and add to the LpiD area

to get 4069.44 x 2 + 2712.96 = 10851.84 cm^2

(It's a strangely shaped "tube" Usually the length is greater than the diameter)