The length of the smaller rectangle is 1/2*40 = <<1/2*40=20>>20 meters.
The width of the smaller rectangle is 1/2*20 = <<1/2*20=10>>10 meters.
Since the area of a rectangle is found by multiplying the length times the width, the total area of the smaller rectangle is 20*10 = <<20*10=200>>200 meters square.
#### 200