Question

The fence around Wayne Manor (a rectangular plot of land) is going to be replaced. No fence will be required for the side lying along Gotham river. If the new wrought iron fence costs $12 per meter for the side parallel to the river and $4 per meter for the other two sides, find the dimensions of the maximum area that can be enclosed by the fence if Bruce Wayne (AKA Batman) cannot spend more than $3600.

Answer 1

If
x = side parallel to river
y = other sides

So, you want to maximize

a = xy
subject to
12x + 4*2y <= 3600

See what you can do with that.

Answer 2

i would like this

Answer 3

300*300