Question

John wants to build a corral next to his barn. He has 300 feet of fencing to enclose three sides of his rectangular yard.

a. What is the largest area that can be enclosed?
b. What dimensions will result in the largest yard?

Answer 1

Let's first define the variables:
x = width
300 - 2x = long
The area will be:
A = (x) * (300 - 2x)
A = 300x - 2x²
We look for the maximum area, for this, we derive:
A '= 300 - 4x
We match zero:
0 = 300 - 4x
x = 300/4 = 75
Therefore, the width is:
x = 75 feet
The length is:
300 - 2x = 300 - 2 (75) = 300-150
150 feet
Answer:
Part A:
The maximum area will be:
A = (150) * (75) = 11250 square feet
Part B:
The dimensions are:
Length = 150 feet
width = 75 feet