Final answer:
The volume of the cylinder is 360 cm³.
Step-by-step explanation:
Given that the cone is 1/3 the size of the cylinder, we can set up a proportion to find the volume of the cylinder. Let's assume the volume of the cylinder is V and the volume of the cone is 120 cm³. Then, we can write the proportion as:
V/120 = 3/1
Cross-multiplying, we get V = 120 x 3 = 360 cm³
Therefore, the volume of the cylinder is 360 cm³.