To find the radius of a circle if only the diameter is given, you simply divide the diameter by 2.

Formula:

$\text{Radius} = \frac{\text{Diameter}}{2}$

Example:

If the diameter $D$ is 12 units (as calculated from the previous problem):

$\text{Radius} = \frac{12}{2} = 6 \text{ units}$

Conclusion:

The radius is half the length of the diameter.

Would you like to explore more on this topic, or do you have any other questions?

---

Here are 5 related questions:

1. What is the diameter if the radius is known to be 7 units?
2. How would you express the circumference of a circle in terms of its radius?
3. Can you derive the area of a circle using the radius?
4. How does doubling the radius affect the diameter?
5. If a circle's radius is increased by 2 units, how does that impact its diameter?

Tip: Understanding the relationship between radius and diameter is crucial, as many circle-related formulas (like circumference and area) use either or both.