Conversion factor, 1 gallon = 4546.09 ml
Volume of stock solution = 1 gallon or 4546.09 ml
Dose required by the child = 5 ml/day
The number of days a gallon of this medicine last,
4546.09 ml x 1 day/ 5 ml = 909.218 days
Therefore, 1 gallon would last 909 days.