12 min read
Introduction
Surface area and volume for boxes, cylinders, cones and spheres — packaging, tanks, and design.
How Much Paint for the Tank?
A cylindrical water tank needs painting on the outside. Paint covers area, not volume — so you need surface area. Filling the tank needs volume.
Solid geometry extends the flat shapes you know (rectangles, circles, triangles) into : faces, nets, and formulas for cuboids, cylinders, cones and spheres.
Example 1 — Cuboid check
A box cm by cm by cm:
Volume = = cm³ Surface area = () = () = cm²
What You Will Practise
You will name solids, draw nets, compute surface area and volume, then tackle cones, spheres, composite solids, density and scaling.
Practice
You must buy wrapping paper for a closed gift box. Which measure do you need?
More lessons in Introduction to Solid Geometry · Next: Naming 3D Solids