Correct Answer - Option 3 : 37500 m²

Let the length of the rectangular field be 10x

Breadth of the rectangular field = 10x × (60/100) = 6x

As we know,

Perimeter of the rectangular field = 2 (l + b)

2 (l + b) = 800

⇒ (10x + 6x) = 400

⇒ 16x = 400

⇒ x = 400/16

⇒ x = 25

Now,

Area of rectangle = l × b

Area of the rectangular field = 10x × 6x

Area of the rectangular field = 60 × 25 × 25 = 37500 m^{2 }

∴ Area of rectangular field = 37500 m^{2}