A rectangular plot of land is to be fenced in using two kinds of fencing. Two opposite sides will use heavy-duty fencing selling for $3 per foot, while the remaining two sides will use standard fencing costing $2 per foot. The budget that will be entirely used for fencing is $6000. In order to maximize the area of the plot, how many feet of standard fencing should be purchased for the project?

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Answer:

1700 ft

Step-by-step explanation:

Let the dimensions of the plot of land be x any y

Where:

  • x is fenced using heavy-duty fencing selling for $3 per foot
  • y is fenced using standard fencing costing $2 per foot.

Perimeter of the Land=2x+2y

Cost of Fencing =$3(2x)+$2(2y)=6x+4y

The budget that will be entirely used for fencing is $6000.

  • Therefore: 6x+4y=6000
  • Make x the subject
  • [tex]x=\dfrac{6000-4y}{6}[/tex]

Area of the Land, A(x,y)=xy

Substitute [tex]x=\dfrac{6000-4y}{6}[/tex] into A(x,y)

[tex]A(y)=\dfrac{6000y-4y^2}{6}\\A'=\dfrac{3000-4y}{3}[/tex]

The Area is maximized when its derivative equals zero.

3000-4y=0

4y=3000

y=750

Recall: [tex]x=\dfrac{6000-4y}{6}=\dfrac{6000-4(750)}{6}=\dfrac{6000-3000}{6}=500[/tex]

Therefore: x=500ft, y=750ft

Since side y is fenced using standard fencing,

Feet of standard Fencing required = 2y=2 X 750 =1500 ft

So, the required length of the sides that have standard fencing is 1500 ft.

Area of the rectangle:

The area of rectangle is the region covered by the rectangle in a two-dimensional plane. A rectangle is a type of quadrilateral, a 2d shape that has four sides and four vertices.

Let [tex]x[/tex] ft be the length of the sides that duty fencing and [tex]y[/tex] ft be the length of the sides that have standard fencing.

So, the area will be calculated by the above formula we get,

[tex]Area=xy[/tex]...(1)

Now, the cost of fencing is,

[tex]3x+2y=6000\\y=3000-\frac{3x}{2}[/tex]...(2)

Now, substituting equation (2) in equation (1) we get,

[tex]A=3000x-\frac{3x^2}{2}[/tex]

Now, differentiating the above equation we get,

[tex]\frac{dA}{dx} =3000-3x=0\\x=1000[/tex]

Substituting [tex]x=1000 ft[/tex] in equation (2) we get,

[tex]y=3000-\frac{3\times 1000}{2}\\=1500 ft[/tex]

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