Area & Perimeter Worksheets | Free - Distance Learning, worksheets ... - Free Printable

To find the area and circumference of a circle, we use two main formulas. We will use $\pi \approx 3.14$ for our calculations.

Formulas:
* Circumference ($C$): The distance around the circle.
* If you have the diameter ($d$): $C = \pi \times d$
* If you have the radius ($r$): $C = 2 \times \pi \times r$
* Area ($A$): The space inside the circle.
* Formula: $A = \pi \times r^2$ (which means $\pi \times r \times r$)

Important Note: Look closely at each problem to see if the number given is the radius (line from center to edge) or the diameter (line all the way across).
* If it is the diameter, divide by 2 to get the radius before finding the Area.

Here are the step-by-step solutions for each problem, rounded to the nearest tenth:

1) Diameter = 2
* Radius ($r$) = $2 / 2 = 1$
* Area: $3.14 \times 1^2 = 3.14 \rightarrow \mathbf{3.1}$
* Circumference: $3.14 \times 2 = 6.28 \rightarrow \mathbf{6.3}$

2) Radius = 8
* Area: $3.14 \times 8^2 = 3.14 \times 64 = 200.96 \rightarrow \mathbf{201.0}$
* Circumference: $2 \times 3.14 \times 8 = 50.24 \rightarrow \mathbf{50.2}$

3) Radius = 15
* Area: $3.14 \times 15^2 = 3.14 \times 225 = 706.5 \rightarrow \mathbf{706.5}$
* Circumference: $2 \times 3.14 \times 15 = 94.2 \rightarrow \mathbf{94.2}$

4) Diameter = 19
* Radius ($r$) = $19 / 2 = 9.5$
* Area: $3.14 \times 9.5^2 = 3.14 \times 90.25 = 283.385 \rightarrow \mathbf{283.4}$
* Circumference: $3.14 \times 19 = 59.66 \rightarrow \mathbf{59.7}$

5) Radius = 6
* Area: $3.14 \times 6^2 = 3.14 \times 36 = 113.04 \rightarrow \mathbf{113.0}$
* Circumference: $2 \times 3.14 \times 6 = 37.68 \rightarrow \mathbf{37.7}$

6) Radius = 4.5
* Area: $3.14 \times 4.5^2 = 3.14 \times 20.25 = 63.585 \rightarrow \mathbf{63.6}$
* Circumference: $2 \times 3.14 \times 4.5 = 28.26 \rightarrow \mathbf{28.3}$

7) Radius = 11.5
* Area: $3.14 \times 11.5^2 = 3.14 \times 132.25 = 415.265 \rightarrow \mathbf{415.3}$
* Circumference: $2 \times 3.14 \times 11.5 = 72.22 \rightarrow \mathbf{72.2}$

8) Diameter = 21
* Radius ($r$) = $21 / 2 = 10.5$
* Area: $3.14 \times 10.5^2 = 3.14 \times 110.25 = 346.185 \rightarrow \mathbf{346.2}$
* Circumference: $3.14 \times 21 = 65.94 \rightarrow \mathbf{65.9}$

9) Diameter = 26
* Radius ($r$) = $26 / 2 = 13$
* Area: $3.14 \times 13^2 = 3.14 \times 169 = 530.66 \rightarrow \mathbf{530.7}$
* Circumference: $3.14 \times 26 = 81.64 \rightarrow \mathbf{81.6}$

10) Diameter = 14
* Radius ($r$) = $14 / 2 = 7$
* Area: $3.14 \times 7^2 = 3.14 \times 49 = 153.86 \rightarrow \mathbf{153.9}$
* Circumference: $3.14 \times 14 = 43.96 \rightarrow \mathbf{44.0}$

Final Answer:
1. Area: 3.1, Circumference: 6.3
2. Area: 201.0, Circumference: 50.2
3. Area: 706.5, Circumference: 94.2
4. Area: 283.4, Circumference: 59.7
5. Area: 113.0, Circumference: 37.7
6. Area: 63.6, Circumference: 28.3
7. Area: 415.3, Circumference: 72.2
8. Area: 346.2, Circumference: 65.9
9. Area: 530.7, Circumference: 81.6
10. Area: 153.9, Circumference: 44.0