Keep in mind that proportion math is an equation where both ratios are equal. In order for everything to work out correctly, all of the terms must be the same. Sometimes it will be necessary to convert grams to milligrams or liters to milliliters, etc.
How many 200mg tablets would be required to make 1.5 liters of a 1:250 solution?
A 1:250 solution would look like this:
So, this question is solved with proportions math: