There are two cones .The curved surface area of one is twice that of the other.

Let the curved surface area of $1^{5 t}$ cone $=2 x$

C.S.A of $2^{\text {nd }}$ cone $=x$

Slant height of $1^{\text {st }}$ cone $=h$

Slant height of $2^{\text {nd }}$ cone $=2 \mathrm{~h}$

Therefore $\frac{\text { C.S. A of } 1^{\text {st }} \text { cone }}{\text { C. S. A of } 2^{\text {nd }} \text { cone }}$

$=2 x / x$

$\Rightarrow \pi r_{1} l_{1} / \pi r_{2} l_{2}=2 / 1$

$\Rightarrow r_{1} / r_{2}=4 / 1$

Therefore ratio of r1 and r2 is 4:1.