Final answer:
To fill the aquarium to the desired depth of 20 inches, 11,520 cubic inches of water are needed.
Step-by-step explanation:
To calculate the amount of water needed to fill the aquarium to a depth of 20 inches, we need to find the volume of the space that the water will occupy using the length and width of the aquarium. Given that the aquarium is 36 inches long and 16 inches wide, with a desired water depth of 20 inches, the volume can be found by multiplying these dimensions together:
Volume = Length × Width × Depth
Volume = 36 inches × 16 inches × 20 inches
Volume = 11,520 cubic inches
To the nearest whole number, you will need 11,520 cubic inches of water to fill the aquarium to the stated depth.