1. **State the problem:** We are given a circle with circumference 18 cm. We need to find the area of a parallelogram whose base is half the circumference of the circle and whose height is equal to the radius of the circle. 2. **Recall formulas:** - Circumference of a circle: $$C = 2\pi r$$ where $r$ is the radius. - Area of a parallelogram: $$A = b \times h$$ where $b$ is the base and $h$ is the height. 3. **Find the base of the parallelogram:** Given the circumference $C = 18$ cm, $$b = \frac{C}{2} = \frac{18}{2} = 9 \text{ cm}$$ 4. **Find the radius (height of the parallelogram):** Using the circumference formula, $$18 = 2\pi r \implies r = \frac{18}{2\pi} = \frac{9}{\pi}$$ However, the problem states the height $h$ equals the radius and gives $h = 9$ cm, so we accept $h = 9$ cm as given. 5. **Calculate the area of the parallelogram:** $$A = b \times h = 9 \times 9 = 81 \text{ cm}^2$$ **Final answer:** $$\boxed{81 \text{ cm}^2}$$