7th Grade · Geometry
Diameter
7.G.B.4
Definition
A chord that passes through the center of a circle, connecting two points on the circle. The diameter is the longest distance across the circle. d = 2r.
Examples
- If r = 5cm, then d = 2(5) = 10cm.
- C = πd = 3.14 × 10 = 31.4 cm.
Key rule
Diameter goes edge to edge through the center; radius goes center to edge.
Memory hook
Diameter is twice the radius, straight across.