Let's solve each of the regular polygons step by step. We'll calculate both
perimeter and
area for each shape using the given information.
---
🔷 General Formulas for Regular Polygons
For a
regular polygon with:
- $ n $ sides
- side length $ s $
- apothem $ a $ (distance from center to midpoint of a side)
Then:
-
Perimeter = $ P = n \times s $
-
Area = $ A = \frac{1}{2} \times P \times a = \frac{1}{2} \times n \times s \times a $
We’ll use these formulas throughout.
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##
✔ Problem 1: Regular Pentagon (Top Left)
Given:
- Side length $ s = 18 $ units
- Apothem $ a = 15 $ units
- Number of sides $ n = 5 $
🔹 Perimeter:
$$
P = 5 \times 18 = 90 \text{ units}
$$
🔹 Area:
$$
A = \frac{1}{2} \times 90 \times 15 = 45 \times 15 = 675 \text{ square units}
$$
✔ Answer:
- Perimeter:
90 units
- Area:
675 square units
---
##
✔ Problem 2: Regular Octagon (Top Right)
Given:
- Side length $ s = 10 $ m
- Apothem $ a = 12.1 $ m
- Number of sides $ n = 8 $
🔹 Perimeter:
$$
P = 8 \times 10 = 80 \text{ m}
$$
🔹 Area:
$$
A = \frac{1}{2} \times 80 \times 12.1 = 40 \times 12.1 = 484 \text{ m}^2
$$
✔ Answer:
- Perimeter:
80 m
- Area:
484 m²
---
##
✔ Problem 3: Regular Octagon (Middle Left)
Given:
- Side length $ s = 5 $ cm
- Apothem $ a = 6 $ cm
- $ n = 8 $
🔹 Perimeter:
$$
P = 8 \times 5 = 40 \text{ cm}
$$
🔹 Area:
$$
A = \frac{1}{2} \times 40 \times 6 = 20 \times 6 = 120 \text{ cm}^2
$$
✔ Answer:
- Perimeter:
40 cm
- Area:
120 cm²
---
##
✔ Problem 4: Regular Hexagon (Middle Right)
Given:
- Side length $ s = 5 $ cm
- Apothem $ a = 4.3 $ cm
- $ n = 6 $
🔹 Perimeter:
$$
P = 6 \times 5 = 30 \text{ cm}
$$
🔹 Area:
$$
A = \frac{1}{2} \times 30 \times 4.3 = 15 \times 4.3 = 64.5 \text{ cm}^2
$$
✔ Answer:
- Perimeter:
30 cm
- Area:
64.5 cm²
---
##
✔ Problem 5: Regular Pentagon (Bottom Left)
Given:
- Side length $ s = 10 $ cm
- Apothem $ a = 6.9 $ cm
- $ n = 5 $
🔹 Perimeter:
$$
P = 5 \times 10 = 50 \text{ cm}
$$
🔹 Area:
$$
A = \frac{1}{2} \times 50 \times 6.9 = 25 \times 6.9 = 172.5 \text{ cm}^2
$$
✔ Answer:
- Perimeter:
50 cm
- Area:
172.5 cm²
---
##
✔ Problem 6: Regular Pentagon (Bottom Right)
Given:
- Side length $ s = 2 $ cm
- Apothem $ a = 1.4 $ cm
- $ n = 5 $
🔹 Perimeter:
$$
P = 5 \times 2 = 10 \text{ cm}
$$
🔹 Area:
$$
A = \frac{1}{2} \times 10 \times 1.4 = 5 \times 1.4 = 7 \text{ cm}^2
$$
✔ Answer:
- Perimeter:
10 cm
- Area:
7 cm²
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📌 Final Answers Summary:
| Shape | Perimeter | Area |
|------|-----------|------|
|
Pentagon (top left) | 90 units | 675 sq units |
|
Octagon (top right) | 80 m | 484 m² |
|
Octagon (middle left) | 40 cm | 120 cm² |
|
Hexagon (middle right) | 30 cm | 64.5 cm² |
|
Pentagon (bottom left) | 50 cm | 172.5 cm² |
|
Pentagon (bottom right) | 10 cm | 7 cm² |
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Let me know if you'd like a visual explanation or help understanding the apothem concept!
Parent Tip: Review the logic above to help your child master the concept of area of regular polygon worksheet.