Final answer:
The correct equation to determine the diameter of a circle based on its radius is Diameter = 2 × Radius.
Step-by-step explanation:
The equation used to determine the diameter of a circle based on its radius is Diameter = 2 × Radius. This is often abbreviated as D = 2r, where 'D' represents the diameter and 'r' represents the radius of the circle.
It is a straightforward formula: Since the diameter is the distance across the circle through the center, it is twice as long as the radius, which is the distance from the center to any point on the circle's edge.