Area and Circumference of a Circle

The area of a circle is calculated using the formula: $$A = \frac{1}{2} \times \text{diameter} \times \text{radius}$$ or $$A = \text{π} \times r^2$$ where r is the radius.

The circumference of a circle is calculated using the formula: $$C = 2 \times \text{π} \times r$$ or $$C = \text{π} \times d$$ where r is the radius and d is the diameter.

The diameter of a circle is twice the length of the radius. This can be expressed as: $$d = 2 \times r$$ .

The diameter is 20 cm, calculated as $$d = 2 \times r = 2 \times 10 = 20 cm$$ .

The radius is 15 m, calculated as $$r = \frac{d}{2} = \frac{30}{2} = 15 m$$ .

The circumference is 43.96 inches, calculated as $$C = 2 \times \text{π} \times 7 \text{ in} \text{ (using } \text{π} \text{ as } 3.14) = 43.96 \text{ in}$$ .

The area is 78.5 square feet, calculated as $$A = \text{π} \times (5)^2 = 78.5 \text{ ft}^2$$ .

The circumference is 37.68 cm, calculated as $$C = \text{π} \times 12 = 37.68 \text{ cm}$$ .

The radius is approximately 3.99 meters, calculated using the area formula: @@A = ext{π} imes r^2 ightarrow r = rac{A}{ ext{π}} = rac{50}{3.14} ightarrow r ext{ is approximately } 3.99 m@@.

The area is 50.24 square inches, calculated as $$A = \text{π} \times (4)^2 = 50.24 \text{ in}^2$$ .