Question

radius =
15

diameter =
30

Explanation:

Step1: Identify given diameter

The given diameter is $30$ mm.

Step2: Calculate radius from diameter

Radius is half the diameter.
$\text{radius} = \frac{\text{diameter}}{2} = \frac{30}{2} = 15$ mm

Step3: Confirm diameter value

The diameter is the given length across the circle.
$\text{diameter} = 30$ mm

Answer:

radius = 15 mm
diameter = 30 mm