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Alligation/Alternate Alligation/Alternate Purpose: An easy method to make a new strength from two existing strengths
| Date post: | 01-Apr-2015 |
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Alligation/AlternateAlligation/Alternate
Purpose:
An easy method to make a new strength from two existing strengths
Sample ProblemSample Problem
Triamcinolone cream is available in strengths of 0.1% and 0.5%. What quantity of 0.1% and 0.5% cream is needed to make 100 grams of 0.2% triamcinolone cream?
Basic Set UpBasic Set Up
% strength starting Material #1
% strength starting Material #2
% strength desired (final product)
% strength starting material #1 minus % strength desired (absolute value)
% strength starting material #2 minus % strength desired (absolute value)
0.1
0.5
0.2
0.3
0.1
% strength starting material #2 minus % strength desired (absolute value)
% strength starting material #1 minus % strength desired (absolute value)
Value is the # of parts needed of starting material #1
Value is the # of parts needed of starting material #2
Total # of parts needed
0.3
0.1 0.1
0.3
0.4
Value is the # of parts needed of starting material #2
Value is the # of parts needed of starting material #1
Total # of parts needed
Total # of parts needed
Ratio needed for starting material #1
Ratio needed for starting material #2
0.3
0.1
0.4
0.4
0.75
0.25
Ratio needed for starting material #1
Ratio needed for starting material #2
Final amount of product desired
Final amount of product desired
Amount needed of starting material #1
Amount needed of starting material #2
0.75
0.25
100 grams
100 grams
75 grams 0.1% cream
25 grams 0.5% cream
AnswerAnswer
75 grams 0.1% cream
25 grams 0.5% cream
100 grams 0.2% cream
Example ProblemExample Problem
How much of a 20% hydrocortisone (HC) cream and how much of a 5% HC cream would be needed to make 50 grams of a 9% HC cream?
Basic Set UpBasic Set Up
20%
5%
9%
11 parts
4 parts
4 parts
11 parts
4 parts
11 parts
15 parts
11 parts
4 parts 15 parts
15 parts
0.267
0.733
50 grams 13.3 grams
36.7 grams
0.267
0.733 50 grams
36.7 grams of 5% HC cream
13.3 grams of 20% HC cream
50 grams of 9% HC cream
Created by:Jeff Sundell &Doug White
