# Solution Mixture Math - Basic Algebra

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There are a few ways to calculate the resulting percentage strength when combining two different strengths of the same type of solution. The examples here are
only for the purpose of studying for the PTCB or ICPT national exams. Do not use the instructions on this page or website in a professional setting or for compounding actual solutions. Please refer to the method your supervising pharmacist issues in a professional environment.

Let's first look at a short video, then an example / practice question
similar to what you might find on the pharmacy Tech Test:

Watch this basic algebra primer video

 Includes: · Proportions Math · Cross Multiplication · C1V1 = C2V2 · Solution Mixtures

You have been asked to take 1.5L / 20% strength solution and combine it into 3.0L / 12.5% strength of the same type of solution. When finished, you will have 4.5L of the solution, but, what percent ?

A. 18%

B. 15%

C. 13%

D. 10%

 % Decimal Qty. Set-up Have 20% .20 1500ml 1500(.20) Have 12.5% .125 3000ml 3000(.125) Unknown ? "X" 4500ml 4500(X)

1) The Equation Set-up:

1500(.20) + 3000 (.125) = 4500X

2) Do the math:

1500(.20) + 3000 (.125) = 4500X

300      +         375        = 4500X

675                     = 4500X

3) Isolate for "X":

 675 = 4500x 4500 4500

4) Solution:

0.15   =   X

You end up with a 15% solution

Solution Mixture Video Tutorial
by Zita Schmitt, CPhT

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