SOL019 · 3D solids & mensuration · Classes 9–10
Sphere surface area
The surface area of a sphere is exactly four times the area of its great circle (Archimedes).
4πr²Sphere surface area
📐 Formula
S = 4πr²; V = 4/3 πr³
✏️ Worked example
r = 3: S = 4 × π × 9 ≈ 113.10.
🌍 Where it is used
Painting domes, making balls, the area of the Earth.
❓ Quick check
Surface area of a sphere of radius 7 (π = 22/7)?
🏋️ Practice
Easyr = 1. S?
Answer: 4π ≈ 12.57
MediumDoubling r multiplies S by…?
Answer: 4
ChallengeArea of a hemisphere's curved surface, r = 7?
Answer: 308 (π = 22/7)