Question 1161939
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A typical setup for solving the problem using formal algebra....<br>
10% of the 12L you start with, plus 4% of the x L you add, yields 6% of the (12+x) L:<br>
{{{.10(12)+.04(x) = .06(12+x)}}}<br>
Solve using basic algebra....<br>
If a formal algebraic solution is not required, here is a quick and easy way to solve mixture problems like this....<br>
You are starting with 10% acid and adding 4% acid until the solution is 6% acid.<br>
Model that by imagining walking on a number line from 10 towards 4, stopping when you get to 6.  What fraction of the distance have you gone?<br>
From 10 to 4 is a distance of 6; from 10 to 6 is a distance of 4.  The fraction of the distance you have gone is 4/6 = 2/3.<br>
That means 2/3 of the final mixture is what you are adding.<br>
So the 12L you started with is 1/3 of the final mixture; and that means the amount of 4% acid you added (2/3 of the final mixture) was 24L.<br>
ANSWER: 24L<br>