1. **Stating the problem:** We need to find the formula for the area of a circle and then calculate the area of two circles: one with radius 8 cm and another with diameter 20 cm. 2. **Formula for the area of a circle:** The area $A$ of a circle is given by the formula: $$A = \pi r^2$$ where $r$ is the radius of the circle. *Important:* The radius is the distance from the center of the circle to any point on its edge. 3. **Calculating the area of the pizza (radius = 8 cm):** - Given radius $r = 8$ cm. - Substitute into the formula: $$A = \pi (8)^2$$ - Calculate the square: $$8^2 = 8 \times 8 = 64$$ - So, $$A = 64\pi$$ This means the area is $64\pi$ square centimeters. 4. **Calculating the area of the circle with diameter 20 cm:** - Diameter $d = 20$ cm. - Radius $r$ is half the diameter: $$r = \frac{20}{2} = 10$$ - Substitute into the formula: $$A = \pi (10)^2$$ - Calculate the square: $$10^2 = 10 \times 10 = 100$$ - So, $$A = 100\pi$$ This means the area is $100\pi$ square centimeters. 5. **Summary:** - Area of pizza = $64\pi$ cm² - Area of circle with diameter 20 cm = $100\pi$ cm² These answers are left in terms of $\pi$ as requested.