Math Problem Statement

Which has a smaller perimeter with the same area of 36 square units, a regular Pentagon, a regular hexagon, a regular octagon

Solution

To compare the perimeters of a regular pentagon, hexagon, and octagon that all have the same area of 36 square units, we first need to express the area and perimeter formulas for these polygons.

Area and Perimeter Formulas

  1. Regular Pentagon:

    • Area (A): A=145(5+25)×s2A = \frac{1}{4} \sqrt{5(5 + 2\sqrt{5})} \times s^2
    • Perimeter (P): P=5sP = 5s
  2. Regular Hexagon:

    • Area (A): A=332×s2A = \frac{3\sqrt{3}}{2} \times s^2
    • Perimeter (P): P=6sP = 6s
  3. Regular Octagon:

    • Area (A): A=2(1+2)×s2A = 2(1 + \sqrt{2}) \times s^2
    • Perimeter (P): P=8sP = 8s

Where ss is the side length of the polygon.

Steps to Compare Perimeters

  1. Solve for the side length ss in each case using the area: spentagon=4A5(5+25)s_{\text{pentagon}} = \sqrt{\frac{4A}{\sqrt{5(5 + 2\sqrt{5})}}} shexagon=2A33s_{\text{hexagon}} = \sqrt{\frac{2A}{3\sqrt{3}}} soctagon=A2(1+2)s_{\text{octagon}} = \sqrt{\frac{A}{2(1 + \sqrt{2})}}

  2. Plug these side lengths into the perimeter formulas: Ppentagon=5×spentagonP_{\text{pentagon}} = 5 \times s_{\text{pentagon}} Phexagon=6×shexagonP_{\text{hexagon}} = 6 \times s_{\text{hexagon}} Poctagon=8×soctagonP_{\text{octagon}} = 8 \times s_{\text{octagon}}

Let's calculate these step by step.The perimeters for each polygon with an area of 36 square units are as follows:

  • Regular Pentagon: Approximately 22.87 units
  • Regular Hexagon: Approximately 22.33 units
  • Regular Octagon: Approximately 21.84 units

Conclusion

The regular octagon has the smallest perimeter when compared to the regular pentagon and hexagon for the same area of 36 square units.

Would you like more details or have any questions?


Here are some related questions you might find interesting:

  1. How do the side lengths compare for these polygons with the same area?
  2. What is the relationship between the number of sides of a polygon and its perimeter for a given area?
  3. How would the perimeters compare for polygons with different areas?
  4. Can this comparison be extended to a regular dodecagon (12 sides)?
  5. How does the shape of the polygon affect its efficiency in enclosing area?
  6. What would happen if the area was increased to 100 square units?
  7. How does the ratio of the perimeter to the area change for these polygons?
  8. What are some real-world applications where minimizing the perimeter for a given area is important?

Tip: Regular polygons with more sides tend to have smaller perimeters for the same area, approaching the characteristics of a circle.

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Math Problem Analysis

Mathematical Concepts

Geometry
Polygons
Area
Perimeter

Formulas

Area of a regular pentagon
Perimeter of a regular pentagon
Area of a regular hexagon
Perimeter of a regular hexagon
Area of a regular octagon
Perimeter of a regular octagon

Theorems

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Suitable Grade Level

Grades 10-12