A typical multivitamin tablet can contain 2.0 mg of vitamin B2 (riboflavin), and the RDA is 0.0030 g/day. How many such tablets should a person take each day to get the proper amount of this vitamin, assuming that he gets none from any other sources?

Suppose that the man does not get Vitamin B2 elsewhere, we can simply divide the amount needed daily by the amout of B2 present in one tablet. Note that the units for the mass are not the same. So, we'll have to convert one first so we can divide them. It will be easier to change the bigger unit to smaller (note that 1 g = 1000 mg) so we have 0.0030 g = 1000 (0.0030) = 3.0 mg. Dividing this value by 2.0 mg, we have 3.0/2.0 = 1.5. Therefore the man must take 1.5 tablets of vitamins daily. Answer: 1.5 tablets