Liana has 800 yards of fencing to enclose a rectangular area. How do you maximize the area?

1 Answer
Feb 19, 2016

Area can be maximized by fencing a square of side 200 yards.

Explanation:

Given perimeter of a rectangle, square has the maximum area (proof given below).

Let x be one of the side and a be te perimeter then the other side would be a/2-x and area would be x(a/2-x) or -x^2+ax/2. The function will be zero when first derivative of the function is equal to zero and second derivative is negative,

As first derivative is -2x+a/2 and this will be zero, when -2x+a/2=0 or x=a/4. Note that second derivative is -2. Then two sides will be a/4 each that the it would be square.

Hence if perimeter is 800 yards and it is a square, one side would be 800/4=200 yards.

Hence area can be maximized by fencing a square of side 200 yards.