When given two percentage solutions, how do you determine the % solution when only two are provided?

To determine the percentage solution when given two percentage solutions, the formula correctly states that the prescribed amount divided by the percentage you want equals the amount you need to mix (xml) divided by the percentage you have. This relationship allows you to set up a proportion that balances the desired outcome with what you currently have on hand.

Essentially, this formula is derived from the concept of creating a solution with a specific concentration by combining two known concentrations. The "prescribed amount" refers to the total volume or weight of the final solution you're trying to achieve, while the "% you want" is the desired concentration of that solution. The "% you have" is the concentration of the available solution you intend to use in the mixture. By formulating it this way, you can easily calculate the volume needed from the higher concentration to reach the target concentration in the final solution.

Using this method ensures that you're accurately combining the two solutions based on their respective concentrations, leading to the precise formulation needed in a pharmacy setting.