The ratio of the radii of two cylinders is 2: 3 and the ratio of their heights is 5: 3. What will be the ratio of their curved surfaces?

Correct option is C

Given:
​$$r_1 : r_2 = 2 : 3,\quad h_1 : h_2 = 5 : 3$$​​
CSA ratio:
​$$\frac{\text{CSA}_1}{\text{CSA}_2}= \frac{2\pi r_1 h_1}{2\pi r_2 h_2}= \frac{r_1 h_1}{r_2 h_2}$$​​
​$$= \frac{2 \times 5}{3 \times 3}= \frac{10}{9}$$​​

Ratio =10 : 9
Correct answer is (C)  ​10 : 9.