Sides of two similar triangles are in the ratio 4 : 9. Areas of these triangles are in the ratio.

here is your answere
If two triangles are similar to each other, then the ratio of the area of this triangle will be equal to the square of the ratio of the corresponding sides of this triangle.
∴ The ratio between area of these triangle= (4)^2/(9)^2=16/81 so we can also say it as 16:81