# Perimeter of 2D shapes ONLY given area?

I'm trying to understand if you can find the perimeter of a shape given only the area of the shape. No length, width, or side.

Square: sqrt(area) * 4 (I think?)

Rectangle: Impossible?

Circle: Possible?

Oval: Impossible?

Equilateral Triangle: Possible?

Oblique or Acute Triangle: Impossible?

Trapezoid: ?

Hexagon: ?

etc.

• No, since there are many shapes with limited area but infinite perimeter. – mathreadler Feb 12 '17 at 17:42
• Can you give an example? And also, if those shapes are rare, what if we were to disregard those shapes? – Hatefiend Feb 12 '17 at 17:43
• The Koch snowflake is famous. But almost any fractal has that property. nl.wikipedia.org/wiki/Koch-kromme – mathreadler Feb 12 '17 at 17:44
• Look for shapes with different perimeters that have the same area. This is straight forward for rectangles. – Karl Feb 12 '17 at 17:44
• @Karl Right right which is why I wrote impossible for Rectangle. So basically, if the shape has all sides of the same length, then it's possible to solve? – Hatefiend Feb 12 '17 at 17:45