You have an aquarium with following characteristics:
w: wide = 18 inches
l: long = 25 inches
h: high = 12 inches
In order to know how many gallons the aquarium has, you first calculate the volume of the aquarium, by using the following formula:
V = w x l x h replace by the given values
V = (18 in) x (25 in) x (12 in) = 5400 in³
Next, you use the following equality:
One gallon of water = 231 in³
You use a simple rule of three to determine how many gallons contain the aquarium:
1 gallon / 231 in³ = x / 5400 in³
where x is the unknown amount of gallons of the aquarium. You solve for x:
x = (5400 in³/231 in³) (1 gallon) = 23.37 gallons of water
23.37 ≈ 23.4
Hence, there are 23.4 gallons of water in the aquarium