Question

A rancher wants to fence in a rectangular area of 14900 square feet in a field and then divide the region in half with a fence down the middle parallel to one side. What is the smallest length of fencing that will be required to do this?

Answer 1

Suppose the length of the fence perpendicular to the central partition is x. Then the total length of the fence (L) for enclosed area A is
.. L = 2x +3*A/x
The derivative of this with respect to x is
.. L' = 2 -3A/x²
L will be minimized when this is zero.
.. 0 = 2 -3A/x²
.. x² = 3A/2
.. x = √(3A/2)

For this value of x, the total length of fence is
.. L = 2√(3A/2) -3A/√(3A/2)
.. L = 4√(3A/2) = 2√(6A)

For this problem, A = 14,900 ft², so
.. L = 2√(6*14,900 ft²) ≈ 597.997 ft

The smallest length of fence required to fence the rectangular area is 598 ft.