Answer :
Because of the correlation of its width and length. In a rectangle length are equal, the same for the width.
No. The area doesn't tell you the dimensions, and you need
the dimensions if you want the perimeter.
If you know the area, you only know the product of the length and width,
but you don't know what either of them is.
In fact, you can draw an infinite number of different rectangles
that all have the same area but different perimeters.
Here. Look at this.
I tell you that a rectangle's area is 256. What is its perimeter ?
-- If the rectangle is 16 by 16, then its perimeter is 64 .
-- If the rectangle is 8 by 32, then its perimeter is 80 .
-- If the rectangle is 4 by 64, then its perimeter is 136 .
-- If the rectangle is 2 by 128, then its perimeter is 260 .
-- If the rectangle is 1 by 256, then its perimeter is 514 .
-- If the rectangle is 0.01 by 25,600 then its perimeter is 51,200.02