Answer: 3πr².
- A 2πr²
- B 3πr²
- C πr²
- D 4πr²
Correct answer: B. 3πr²
Explanation: TSA of hemisphere = curved SA + base = 2πr² + πr² = 3πr².
Three standard 3D solids and their key formulas: a cylinder's volume scales with the full height, a cone's volume is exactly one-third of the cylinder with the same base and height, and a sphere's volume and surface area both follow distinct r-based formulas worth memorising separately.
Concept context
Perimeters, areas, and volumes of 2D and 3D shapes