Question 1081001
.
How much pure disinfectant must be added to 30 gallons of an 8% solution to increase its strength {{{highlight(cross(of))}}} to 25%? 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~


<pre>
Let x be the volume of the pure disinfectant under the question, in gallons.

Then the volume of the new mixture will be (30 + x) and the volume content of the pure disinfectant in the new mixture 
     will be 0.08*30 + x gallons.


So, the concentration equation is

{{{(0.08*30 + x)/(30+x)}}} = 0.25.

Simplify and solve it for x:

2.4 + x = 0.25*(30+x),

2.4 + x = 7.5 + 0.25x,

x - 0.25x = 7.5 - 2.4,

0.75x = 5.1  ---->  x = {{{5.1/0.75}}} = 6.8.


<U>Answer</U>.  6.8 gallons of the pure disinfectant must be added.
</pre>

There is entire bunch of lessons covering various types of mixture problems

&nbsp;&nbsp;&nbsp;&nbsp;- <A HREF=http://www.algebra.com/algebra/homework/word/mixtures/Mixture-problems.lesson>Mixture problems</A>

&nbsp;&nbsp;&nbsp;&nbsp;- <A HREF=http://www.algebra.com/algebra/homework/word/mixtures/More-Mixture-problems.lesson>More Mixture problems</A>

&nbsp;&nbsp;&nbsp;&nbsp;- <A HREF=http://www.algebra.com/algebra/homework/word/mixtures/Solving-typical-mixture-problems.lesson>Solving typical word problems on mixtures for solutions</A> 

&nbsp;&nbsp;&nbsp;&nbsp;- <A HREF=https://www.algebra.com/algebra/homework/word/mixtures/Word-problems-on-mixtures-for-antifreeze-solutions.lesson>Word problems on mixtures for antifreeze solutions</A> 

&nbsp;&nbsp;&nbsp;&nbsp;- <A HREF=https://www.algebra.com/algebra/homework/word/mixtures/Word-problems-on-mixtures-for-alloys.lesson>Word problems on mixtures for alloys</A> 

&nbsp;&nbsp;&nbsp;&nbsp;- <A HREF=https://www.algebra.com/algebra/homework/word/mixtures/Typical-word-problems-on-mixtures-from-the-archive.lesson>Typical word problems on mixtures from the archive</A>

in this site.


Read them and become an expert in solution the mixture word problems.


Also, you have this free of charge online textbook in ALGEBRA-I in this site

&nbsp;&nbsp;&nbsp;&nbsp;- <A HREF=https://www.algebra.com/algebra/homework/quadratic/lessons/ALGEBRA-I-YOUR-ONLINE-TEXTBOOK.lesson>ALGEBRA-I - YOUR ONLINE TEXTBOOK</A>.


The referred lessons are the part of this textbook in the section "<U>Word problems</U>" under the topic "<U>Mixture problems</U>".