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A circle, square, equilateral triangle and regular pentagon have the same areas. Arrange the following in ascending order based on their perimeters.
(A) Circle
(B) Square
(C) Equilateral triangle
(D) Regular pentagon
A circle is the most efficient shape — it covers the most area for a given perimeter, or needs the least perimeter for a given area.
As a regular polygon gets more sides, it starts to resemble a circle, and its perimeter for the same area becomes smaller.
1. Equilateral Triangle (3 sides): Fewest sides, largest perimeter.
2. Square (4 sides): More sides, smaller perimeter than a triangle.
3. Regular Pentagon (5 sides): More sides, smaller perimeter than a square.
4. Circle (infinite sides): Most efficient, smallest perimeter for given area.
Therefore, the perimeters in ascending order are:
(A) Circle < (D) Regular pentagon < (B) Square < (C) Equilateral triangle.