Question

The ratio of radii of two cone is 1 : 36 and the ratio of their slant height is 1 : 7.then, find the ratio of their curved surface area.
1. 1 : 252
2. 7 : 167
3. 2 : 11
4. 67 : 89

Answer 1

Correct Answer - Option 1 : 1 : 252

Given

Ratio of radii of two cones = 1 : 36

Ratio of slant height of two cones = 1 : 7

Formula used 

Curved surface area of cone = πrl

Where r and l are radius and slant height of a cone respectively.

Calculation

CSA₁/CSA₂= πRL/πrl

Where R and r radius of first and second cone

CSA1/CSA2 = (1/36) × (1/7)

CSA1/CSA2 = 1 : 252

∴ The ratio of the two curved surface area of a cone is 1 : 252.