Question 30391
First off, real my Lesson on this website on how to do this type of question.


Second, just looking at the question, we have some 10% and some 1% that mix to make a 2% solution.


Just by common sense, we will need more of the 1% solution, since the final answer is a 2% solution. Hoepfully that makes sense? We expect a lot more of the 1% solution to be used.


Right...
Let x = amount of 1% solution used.
So, how much of 10% is used? Answer is (15-x) --> ie everything else to make up the final 15ml.


BEFORE: x of 1% AND (15-x) of 10%
--> 0.01x + 0.10(15-x)


AFTER: 15ml of 2%
--> 0.02*15


And being a mixture, the BEFORE has to equal the AFTER:
0.01x + 0.10(15-x) = 0.02*15
0.01x + 1.5 - 0.10x = 0.30
-0.09x = -1.2
x = -1.2/-0.09
x = 13.3333 ml


and so there are 13.3333ml of the 1% solution and 1.6666ml of the 10% solution.


jon.