It could be anything.

Answer 1

It is a polygon, whose area is 64. If the length is "x" and the height is "y" and it is a square, then the area is x times y is 64. If it is not a square, then the formulas get a bit more complicated, but the concept is the same.

That is all true, but the question asks for a length. If you mean perimeter, that depends entirely on the shape of the polygon. If it is a square, and x and y are as above, then x equals y equals 8 meters, and the perimeter is 8 times 4 or 32 meters. If it is a rectangle, the perimeter will be at least 32 meters but there is no limit to how high the perimeter can be. For example, if x is 1 millimeter, then y has to be 64,000 meters or 64 kilometers, and the perimeter is 128,000.002 meters.