2018 · Q68
If the ratio of the radius of the base of a right circular cone to its slant height is 1:3, what is the ratio of the total surface area to the curved surface area?
Elementary MathematicsMensuration
- A5:3
- B3:1
- C4:1
- D4:3
Explanation
With r : l = 1 : 3, total surface area = πr(r + l) = 4πr² and curved surface area = πrl = 3πr². Their ratio is 4 : 3, option (D).