Choose the correct answer in each of the following :
The curved surface area of one cone is twice that of the other while the slant height of the latter is twice that of the former. The ratio of their radii is
(a) 2:1 (b) 4:1 (c) 8:1 (d) 1:1
The curved surface area of the cone is π × r × l
So,
Curved surface area of 1 st cone = π × r1 × l1
Curved surface area of 2 nd cone = π × r2 × l2
Given, the curved surface area of 1 st cone is twice of the curved surface area of 2 nd cone
π × r1 × l1 = 2 π × r2 × l2
r1 × l1 = 2 r2 × l2
l2 = 2l1
r1 × l1 = 2 x r2 × 2 × l1
r1r2 = 4:1
(b) 4:1