If you have a fixed perimeter you can consider having a fence, and ask how big of a area it would surround. notice that if you were to enclose an areas with a fixed length the areas can vary greatly.
You can have a really really long length and a very short height (like a piece of spaghetti) versus a square which would have a much larger area.... Note in a calculus class you can take the derivative of the area function given a fixed perimeter, and you can calculate the maximum area you can get. Fixed area would be the inverse saying that you can get a bunch of different perimeters even if you keep the area constant. (Photo attached)
