The radius of a circle is the distance from the center to any point on the circumference. The diameter is the distance from one side of the circle's circumference, through the center of the circle, to the opposite side.
Let's recall the definitions of radius and diameter.
Radius: Distance from the center of the circle to any point on the circumference.
Diameter: Distance from one side of the circle's circumference, through the center of the circle, to the opposite side.
We can see in the diagram that the radius is 10inches. According to the definitions, the diameter is twice the radius. Therefore, the diameter is 10* 2=20inches.
