a rectangular field is to be enclosed by a fence. two fences, parallel to one side of the field, divided the field into 3 rectangular fields. if 2400 m of fence is available find the dimensions of the field giving the maximum area.

Answer 1

as always, divide the fence equally among lengths and widths.
You have 2 lengths and 4 widths.
So, allocating 1200m to each, the dimensions are

1200/2 x 1200/4 = 600 x 300

Or, you can go through the math, using
2x + 4y = 2400
a = xy
and finding the maximum value for a