This document discusses various pharmaceutical calculations related to concentration and dilution. It defines percent, ratio strength, and different types of concentrations including weight/volume, weight/weight, and volume/volume. It also covers topics such as dilutions, alligations, and alligations alternate. Dilutions are used to create lower concentration solutions from more concentrated stock solutions. Alligations and alligations alternate are methods to calculate new concentrations or volumes when combining solutions of different concentrations.