Hello,

let w be the width of the rectangle and

l be the length of the rectangle.

Then the area is calculated by:

[1]

the fence f consists of . Since f = 480 you get:

[2]

Plug in the term for l into the equation[1]:

This is a parabola opening downward, the maximum value is at it's vertex:

and

You'll get: w = 120 m and l = 240 m. The maximum area is 28800 mē