Problema Solution

A rancher has 296 feet of fencing to enclose two identical adjacent rectangular corrals that share a side. What dimensions (for the individual corrals) will produce the largest total area? What is the maximum total area (in square feet)?

Answer provided by our tutors

let 'x' and 'y' be the sides of the rectangular corral.


let 'x' be the side the 2 adjacent corrals share.


since the perimeter of 2 corrals together is 296 ft we can write


x + y + y + x + y + y = 296


2x + 4y = 296 divide both sides by 2


x + 2y = 148 => y = 74 - (x/2)


the area of the 2 corrals together is


A = x*(2y) = 2xy


if we replace for y = 74 - (x/2) we get


A = 2x * (74 - (x/2))


A = 148x - x^2


The quadratic function A(x) = 148x - x^2 = -x^2 + 148x + 0 has maximum at its vertex (since the quotient in front of x^2 is negative) that is


A max = 0 - 148^2/ 4*(-1) = 5476 ft^2


and by solving the quadratic


-x^2 + 148x = 5476


-x^2 + 148x - 5476 = 0


we find


x = 74 ft


y = 74 - (x/2)


y = 74 - (74/2)


y = 74 - 37


y = 37 ft


The maximum total area is 5476 ft^2.

The dimensions for the individual corral is 74 ft and 37 ft.