Answer:
5000 sq. meters.
Explanation:
Let the length of the rectangle is L m and width is W m.
Now, if the fourth side is a length of the rectangle, then by the condition given,
L + 2W = 200
⇒ L = 200 - 2W
Now, area of the rectangle is A = LW = (200 - 2W)W
For, area to be maximum the condition is

⇒ W = 50 m.
Then, L = 200 - 2W = 100 m.
Therefore, the maximum are is
sq. meters. (Answer)