SOLUTION: I really need help with this one. A chemist wants to combine a solution that is 30% glycerin with pure 100% glycerin. He wants to produce 42 milliliters of a solution that is 50%

Question 23493: I really need help with this one. A chemist wants to combine a solution that is 30% glycerin with pure 100% glycerin. He wants to produce 42 milliliters of a solution that is 50% glycerin. How much of the 30% solution and how much of the pure glycerin should the chemist use? Thank you so very much for your help!
Answer by longjonsilver(2297) (Show Source): You can put this solution on YOUR website!
very simple premise in this type of question..just keep focussed. Also, look at my Lesson on this website, that explains my process better.

Anyway: We need to know how much of the 30% solution we need..so let this be x.

Now..the crucial bit. How much of the 100% solution is therefore used? Sneaky... answer is THE REST of the 42ml, in other words, 42-x.

So, we have 0.30x + 1.00(42-x) = 0.50*42 ... this is the maths version of te question. Make sure you see how this comes about.. it is simple really, all Mixture questions are IDENTICAL to this (more or less lol).

Anyway, 0.30x + 42 - x = 21
0.30x + 42 - x = 21
-0.7x = -21
x = -21/-0.7
x = 30ml

So, 30ml of the 30% glycerin
and (42-30) --> 12ml of the 100% glycerin.

OK?

jon.

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