How many gallons of water are in a fish tank that is 20 x 20 x 99?

To find the volume of a fish tank that measures 20 inches by 20 inches by 99 inches, first calculate the volume in cubic inches: (20 \times 20 \times 99 = 39,600) cubic inches. Since there are 231 cubic inches in a gallon, divide the total volume by 231: (39,600 \div 231 \approx 171) gallons. Therefore, the fish tank holds approximately 171 gallons of water.