8th Grade · Geometry
Sphere
8.G.C.9
Definition
A perfectly round three-dimensional solid where every surface point is equidistant from the center. Its volume is four-thirds times pi times the radius cubed.
Examples
- V = (4/3)π(3)³ = 36π ≈ 113.1 cubic units.
- Every point on the surface is the same distance r from the center.
Key rule
Sphere volume uses r cubed, since a sphere fills three dimensions.
Memory hook
Perfectly round, volume uses r cubed.