The total capacity of the pool = 18000 gallon The total volume of the pool when calculated to 2/5 = (2/5) * 18000 = 35000/5 gallons = 7200 gallons. Now it is given in the problem that that Rate at which the pool is filled with water = 20 gallons per minutes Then 20 gallons of water is filled in = 1 minute So 7200 gallons of water will be filled in = 7200/20 minute = 720/2 minute = 360 minute So 360 minute is required to fill the pool with 2/5 of the total volume of water.
