The ratio of the areas of two similar triangles is 81:4. The ratio of their corresponding sides is

Given that, the ratio of areas of two similar triangles is 81:4.

We know that the ratio of the areas of two similar triangles is equal to the square of the ratio of their corresponding sides.

∴ The ratio of the corresponding sides of the similar triangles $=\sqrt{\frac{81}{4}}=\frac{9}{2}$

Hence, the required ratio of their sides is 9:2.