The diameters of two cones are equal. If their slant heights

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The diameters of two cones are equal. If their slant heights be in the ratio of 5 : 7, then find the ratio of their curved surface areas. ?

1. 25 : 7
2. 25 : 49
3. 5 : 49
4. 5 : 7

Correct Option: D

Given, l₁/l₂ = 5/7
Now, curved surface area of the first cone = π rl₁
and curved surface area of second cone = πrl₂
∴ Ratio = πrl₁/πrl₂ = l₁/l₂ = 5 : 7