
208 Chapter 5
diameter is double the radius
How big are the pizzas that MegaSlice are cutting up and selling by
the slice?
The pizza must be as wide as two
of the slice edges—12 inches.
The diameter of a pizza is twice its radius
The total width of the pizza—12 inches—is a special circle property we
call diameter. The diameter of a circle is the distance from one side to the
other, passing through the center. The length of the edge of the pizza slice
is called radius, and is the distance from the center to any point on the
edge. Diameter is always two times the radius.
It doesn’t matter which points on
the edge you draw your diameter
between, or where you draw the
radius to, it’s always the same size
(just remember to include the center).
Diameter
Radius
The diameter and radius always include
the center of the circle.
6”
6”
12”
circle
Diameter is always
twice the radius:
D = 2r