Question

A rectangular pen for pigs that will enclose a total area of 169 square feet. What is the least amount of fencing that is needed?

Answer 1

The answer is below

Explanation:

Let x represent the length of the rectangular pen and y represent the width of the rectangular pen. Since the total area of the pen is 169 ft², hence:

Area = length * width

169 = xy

y = 169/x

Also the perimeter of the rectangular pen is:

Perimeter (P) = 2(length + width)

P = 2(x + y)

P = 2x + 2y

P = 2x + 2(169/x)

P = 2x + 338/x

The least amount of fencing is at dP/dx = 0, hence:

dP/dx = 2 - 338/x² = 0

338/x² = 2

2x² = 338

x² = 169

x = 13 feet

y = 169 / x = 169/13 = 13 feet

The least amount of fencing = P = 2(x + y) = 2(13 + 13) = 52 feet