Circle — The radius is 3 cm. Find the diameter.

Introduction / Context:
Diameter is twice the radius. This is a direct one-step geometry fact used frequently in circle problems.

Given Data / Assumptions:

• r = 3 cm

Concept / Approach:
d = 2 * r.

Step-by-Step Solution:
d = 2 * 3 = 6 cm

Verification / Alternative check:
None needed beyond the definition.

Why Other Options Are Wrong:
12 cm doubles twice; 1.5 cm is half the radius; 8 and 9 cm are unrelated.

Common Pitfalls:
Mixing up radius and diameter roles.

Final Answer:
6 cm