Radius and diameters depend on the circles you draw. For example,
Small circle: Radius 1.5 cm Diameter 3 cm
Medium circle: Radius 2.3 cm Diameter 4.6 cm
Large circle: Radius 3 cm Diameter 6 cm
What is the relationship between the radius and diameter of each circle?
The diameter is 2 times the radius.
Is that true for any circle? Talk about it: Why do you think so?
Because the diameter goes through the center, it is made up of two radii that start in the center. These radii are the same length. So a diameter has to be twice as long as a radius. This will be true no matter what size the circle is, because you can draw a diameter and two radii that make it up.