Answer: 3154.16 milliliters / second
Explanation:
1 gallon = 3.785 liters
1 liter = 1000 milliliters.
So multiply to convert: 1 gallon x 3.785 liters/gallon x 1000 milliters/liter = 3785 milliters ; 50 gallons = 50*3785 = 189250 milliliters
1 hr = 60 seconds 50 gallons per hour = 189250 mililiters/60 seconds =3154.16 milliliters/second
result : 50 gallons per hour = 3154.16 milliliters / second