Circumference and Area of Circles

$$A=\frac{1}{2}\times\text{diameter}\times\text{height}$$ or $$A=\text{π} \times r^2$$ where r is the radius.

$$C=2\text{π}r$$ or $$C=\text{π}d$$ where d is the diameter.

@@A= ext{π} imes (7)^2 \\ A ext{ is approximately } 153.94 ext{ cm}^2.

@@C= ext{π} imes 10 \\ C ext{ is approximately } 31.42 ext{ cm}.

The diameter is twice the radius: $$d=2r$$ .

To find the radius, divide the diameter by 2: $$r=\frac{d}{2}$$ .

@@A= ext{π} imes (5)^2 \\ A ext{ is approximately } 78.54 ext{ cm}^2.

@@C=2 ext{π} imes 3 \\ C ext{ is approximately } 18.85 ext{ cm}.

@@A= ext{π} imes r^2 \\ r=rac{A}{ ext{π}} \\ r ext{ is approximately } 4.01 ext{ cm}.

@@A= ext{π} imes (4)^2 \\ A ext{ is approximately } 50.27 ext{ cm}^2.