Geometry

Question Analysis:
This question involves a composite solid (cylinder + cone).
The main focus is calculating the combined volume and solving for radius, using known geometric formulas.

Key Concept Explanation:
Volume of a cylinder:
Volume of a cone:
Since the cylinder’s height equals its radius, and the cone has the same radius and height, both volumes will use the same variable r.

Step-by-Step Solution:
Let the radius = r
Cylinder volume:
Cone volume:
Total volume: