Final answer:
To find the water density per square foot, multiply the garden's dimensions to get the area in square feet, convert gallons to cubic feet, then divide water volume by garden area, resulting in a density of 0.08355 cubic feet per square foot.
Step-by-step explanation:
The question asks to determine the density of water used per square foot in a rectangular garden that Philip waters with 20 gallons of water each week. The garden is described as being 4 feet in width and 8 feet in length. To compute the density, we first calculate the area of the garden by multiplying its length by its width: 4 feet (width) × 8 feet (length) = 32 square feet. Next, we convert the 20 gallons of water to cubic feet because 1 gallon is approximately 0.133681 cubic feet. Therefore, 20 gallons × 0.133681 cubic feet/gallon = 2.67362 cubic feet. Finally, to find the density of water per square foot, we divide the volume of water by the area of the garden: 2.67362 cubic feet / 32 square feet = 0.08355 cubic feet per square foot.