Final answer:
The ratio of the heights of the two similar cylinders is 2:1.
Step-by-step explanation:
To find the ratio of the heights of two similar cylinders, we need to consider the relationship between their radii.
Let's assume the radii of the two cylinders are 2x and x, where x is a positive number. Since the cylinders are similar, their heights will also be in the same ratio as their radii. Therefore, the ratio of their heights is 2x:x, which simplifies to 2:1.