<PRE><B>Question 53186</B>
When you do these, think about this:
You have 2L 20% acid solution and 3L 40% acid solution, what is the total percentage of acid? Hint: use the mean.
{{{(0.2 + 0.2 + 0.4 + 0.4 + 0.4)/(5) = (2(0.2) + 3(0.4))/5 = 0.32}}}
You would multiply amount of Liters by the acid quality and divide by the total amount of Liters to get a 32% acid solution. Put more simply, you are finding the MEAN.
Now, let me answer your question.
x = the amount of Liters of 10% alcohol solution
10 - x = the amount of Liters of 30% alcohol solution
{{{(x(0.1) + (10 - x)(0.3))/10 = 0.25}}}
{{{0.1x + 3 - 0.3x = 2.5}}}
{{{-0.2x = -0.5}}}
{{{x = 2.5}}}
10 - 2.5 = 7.5
2.5L of 10%
7.5L of 30%</PRE>