1. **State the problem:** We need to find the diameter of a circle when the radius is given as 6 centimeters. 2. **Recall the formula:** The diameter $d$ of a circle is twice the radius $r$. Mathematically, this is expressed as: $$d = 2r$$ 3. **Apply the formula:** Given $r = 6$ cm, substitute into the formula: $$d = 2 \times 6$$ 4. **Calculate the diameter:** $$d = 12$$ 5. **Interpretation:** The diameter of the circle Russell drew is 12 centimeters. This follows from the ratio of radius to diameter being 1 to 2, meaning the diameter is always twice the radius.