Question: how to make a 1 to 200 dilution?
Answer: For example, you want a 1/10,000 dilution of whole serum (undiluted) and you need 50 ml. 200 (1/200 dilution) = the first step in the dilution factor; the second is 1/50, obtained as follows: 1 ml of serum + 199 ml of diluent = 1/200 dilution.