Question

Amy wants to fence off a rectangular area that is 24 feet squared in size for a vegetable garden.

She is considering three garden lengths of 6 ft, 8 ft, and 12 ft. She wants to determine which garden would require the least amount of fencing.
Determine the dimensions of the garden that would require the least amount of fencing.

Length
12, 8, or 6ft
Width:
3, 4, or 2ft

Answer 1

Let y = length of side parallel to the side with no fence

x = length of each of the other two sides

Then, y+2x = 64. So, y = 64-2x

Area = A = xy = x(64-2x)

The graph of the area function is a parabola opening downward with a highest point and with x-intercepts (0,0) and (32,0).

By the symmetry of the parabola, the x-coordinate of the maximum point lies halfway between the x-intercepts.

So, the area is maximized when x = 16 ft

y = 64 - 2x = 32 ft

Maximum area = xy = (16)(32) = 512 ft2

To maximize the area of the garden, the side of the fence parallel to the side of the house should be 32 ft long, and the other two sides should both have length 16 ft.