Are milligrams kilograms and gallons liquid measurements?
No. Milligrams and kilograms are measures of weight or mass. Gallons is a measure of volume.
You just put a units after the volume that you found. Also, weight(lbs, oz, ect.) count as value and so to liquid measurements(gal, pint, ect.) When you are doing weight or liquid measurements, just use the unit. For example, if you find the amount of liquid inside a cylinder, and the answer is 90 gallons, you just use gallons, nothing else
If you have fifteen gallons of liquid and you have to add one quart of water per one hundred gallons how much water would you add to your fifteen gallons of liquid?
There are different fractions of mineral oil, commonly divided into light and heavy. But if we assign a density of about 0.8 g/ml to this liquid petrolatum, we'll discover that 170 kilograms is about 56.14 gallons. You have 170,000 grams of mineral oil. Divide that by 0.8, then divide that by 3785.4 (which is the number of ml in a gallon) and this will be your answer.
Milligrams is a metric measure of mass. Gallons is an English measure of liquid volume. While you could do the conversion you would first need to know what liquid you were converting. Milk, gasoline, water they all have different mass per gallon. A milligram is a very small amount of any of these. 1 milligram = 1/1000th of a gram.