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Find the perimeter and apothem of each polygon based on given area and side length.

Worksheet with nine polygons, each labeled with area and side length, asking to find perimeter and apothem.

Worksheet with nine polygons, each labeled with area and side length, asking to find perimeter and apothem.

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Show Answer Key & Explanations Step-by-step solution for: Apothem of Polygons Using Area Worksheets
Let's solve each problem step by step using the formula for the area of a regular polygon:

$$
\text{Area} = \frac{1}{2} \times \text{Perimeter} \times \text{Apothem}
$$

We can rearrange this formula to solve for perimeter and apothem:

- $ \text{Perimeter} = \frac{2 \times \text{Area}}{\text{Apothem}} $
- $ \text{Apothem} = \frac{2 \times \text{Area}}{\text{Perimeter}} $

But in these problems, we are given:
- The area
- The side length (or implied from shape and label)
- And the number of sides (from the shape)

So we’ll use:
- Perimeter = number of sides × side length
- Then use the area formula to find the apothem.

---

Let’s go through each one.

---

1) Pentagon



- Side = 7.5 yd
- Area = 337.21 yd²
- Number of sides = 5

Perimeter = $ 5 \times 7.5 = 37.5 $ yd

Now use area formula:

$$
\text{Area} = \frac{1}{2} \times P \times a \Rightarrow 337.21 = \frac{1}{2} \times 37.5 \times a
$$

$$
337.21 = 18.75a \Rightarrow a = \frac{337.21}{18.75} \approx 18.00
$$

Perimeter: 37.50 yd, Apothem: 18.00 yd

---

2) Hexagon



- Side = 6 ft
- Area = 93.53 ft²
- Sides = 6

Perimeter = $ 6 \times 6 = 36 $ ft

$$
93.53 = \frac{1}{2} \times 36 \times a = 18a \Rightarrow a = \frac{93.53}{18} \approx 5.196 \approx 5.20
$$

Perimeter: 36.00 ft, Apothem: 5.20 ft

---

3) Octagon



- Side = 11 in
- Area = 439.7 in²
- Sides = 8

Perimeter = $ 8 \times 11 = 88 $ in

$$
439.7 = \frac{1}{2} \times 88 \times a = 44a \Rightarrow a = \frac{439.7}{44} \approx 9.993 \approx 9.99
$$

Perimeter: 88.00 in, Apothem: 9.99 in

---

4) Triangle (Equilateral)



- Side = 8 ft
- Area = 35.07 ft²
- Sides = 3

Perimeter = $ 3 \times 8 = 24 $ ft

$$
35.07 = \frac{1}{2} \times 24 \times a = 12a \Rightarrow a = \frac{35.07}{12} \approx 2.9225 \approx 2.92
$$

Perimeter: 24.00 ft, Apothem: 2.92 ft

---

5) Octagon



- Side = 13 in
- Area = 1,044.73 in²
- Sides = 8

Perimeter = $ 8 \times 13 = 104 $ in

$$
1044.73 = \frac{1}{2} \times 104 \times a = 52a \Rightarrow a = \frac{1044.73}{52} \approx 20.091 \approx 20.09
$$

Perimeter: 104.00 in, Apothem: 20.09 in

---

6) Heptagon (7 sides)



- Side = 8 yd
- Area = 309.01 yd²
- Sides = 7

Perimeter = $ 7 \times 8 = 56 $ yd

$$
309.01 = \frac{1}{2} \times 56 \times a = 28a \Rightarrow a = \frac{309.01}{28} \approx 11.036 \approx 11.04
$$

Perimeter: 56.00 yd, Apothem: 11.04 yd

---

7) Nonagon (9 sides)



- Side = 3 in
- Area = 192.36 in²
- Sides = 9

Perimeter = $ 9 \times 3 = 27 $ in

$$
192.36 = \frac{1}{2} \times 27 \times a = 13.5a \Rightarrow a = \frac{192.36}{13.5} \approx 14.249 \approx 14.25
$$

Perimeter: 27.00 in, Apothem: 14.25 in

---

8) Pentagon



- Side = 20 yd
- Area = 688.15 yd²
- Sides = 5

Perimeter = $ 5 \times 20 = 100 $ yd

$$
688.15 = \frac{1}{2} \times 100 \times a = 50a \Rightarrow a = \frac{688.15}{50} = 13.763 \approx 13.76
$$

Perimeter: 100.00 yd, Apothem: 13.76 yd

---

9) Square



- Side = 12 ft
- Area = 144 ft²
- Sides = 4

Perimeter = $ 4 \times 12 = 48 $ ft

$$
144 = \frac{1}{2} \times 48 \times a = 24a \Rightarrow a = \frac{144}{24} = 6.00
$$

Perimeter: 48.00 ft, Apothem: 6.00 ft

---

Final Answers (Rounded to Two Decimal Places):



| Problem | Perimeter | Apothem |
|--------|-----------|---------|
| 1) | 37.50 yd | 18.00 yd |
| 2) | 36.00 ft | 5.20 ft |
| 3) | 88.00 in | 9.99 in |
| 4) | 24.00 ft | 2.92 ft |
| 5) | 104.00 in | 20.09 in |
| 6) | 56.00 yd | 11.04 yd |
| 7) | 27.00 in | 14.25 in |
| 8) | 100.00 yd | 13.76 yd |
| 9) | 48.00 ft | 6.00 ft |

---

🔍 Explanation Summary:



For regular polygons, you can always use:
- Perimeter = n × s (n = number of sides, s = side length)
- Area = (1/2) × Perimeter × Apothem
- So: Apothem = (2 × Area) / Perimeter

This method works because the apothem is the distance from the center to the midpoint of a side, and it acts as the height of each of the congruent triangles that make up the polygon.

Let me know if you'd like a visual explanation or formulas!
Parent Tip: Review the logic above to help your child master the concept of area of a regular polygon worksheet.
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