In a cylindrical vessel, the liquid level reaches 18 cm. At what height will the liquid level

In a cylindrical vessel, the liquid level reaches 18 cm. At what height will the liquid level be if it is poured into a second vessel, the diameter of which is 3 times the first?

The volume occupied by the liquid is equal to the product of the area of the base of the cylinder by its height:
V = h * S = h * (Pi * D ^ 2) / 4
After the transfusion, the height became h1, and the diameter D1 = 3D.
At the same time, the volume has not changed.
V = h1 * S1 = h1 * (Pi * D1 ^ 2) / 4 = h1 * (Pi * (3D) ^ 2) / 4 = h1 * (Pi * 9D ^ 2) / 4
The left sides of the obtained equalities are equal, so we can write down the equality of the right sides:
h * (Pi * D ^ 2) / 4 = h1 * (Pi * 9D ^ 2) / 4
After cancellation by (Pi * D ^ 2) / 4 we get:
h = 9 * h1
h1 = h / 9 = 18 cm / 9 = 2 cm.

Answer: 2 cm.