SOLUTION: A pharmacist wishes to mix a solution that is 7% Minoxidil. She has on hand 70 ml of a 2% solution and wishes to add some 9% solution to obtain the desired 7% solution
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Question 1136343: A pharmacist wishes to mix a solution that is 7% Minoxidil. She has on hand 70 ml of a 2% solution and wishes to add some 9% solution to obtain the desired 7% solution. How much 9% solution should she add? Found 2 solutions by josmiceli, greenestamps:Answer by josmiceli(19441) (Show Source):
You can put this solution on YOUR website! Let = ml of 9% solution to be added
175 ml of 9% solution should be added
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check: ( 7% )
OK
Here is an alternative to the traditional algebraic method for solving mixture problems like this. It will get you to the answer much faster, if you understand how to use it.
You are starting with 70ml of a 2% solution and adding some 9% solution; you want to stop when the mixture is 7%.
(1) Looking at the percentages, 7 is 5/7 of the way from 2 to 9. [9-2=7; 7-2=5; (7-2)/(9-2) = 5/7)]
(2) That means 5/7 of the mixture must be what you are adding.
(3) That means 2 parts of the original to 5 parts of what you are adding.
(4) The amount of 9% solution you need to add is (70)*(5/2) = 175ml.
