Question 1124591
.
<pre>
The amount of the pure alcohol in 1.75 L of the 18% solution is  0.18*1.75 liters = 0.315 liters.


This volume of the pure alcohol will not change and will remain the same after adding water.


So, you need to add, let say, x liter of water to get


   {{{0.315/(0.315+x)}}} = 0.05   (which is 5% of concentration of the final mixture)


So, you need solve this equation.


For it, multiply the both sides of the equation by (0.315+x) to get


    0.315 = 0.05*(0.315 + x).


Simplify and solve for x:


    0.315 = 0.05*0.315 + 0.05x

    0.315 - 0.05*0.315 = 0.05x


    x = {{{(0.315 - 0.05*0.315)/0.05}}} = 5.985.


<U>Answer</U>.  You need to add  5.985 liters of water.


<U>Check</U>.   {{{0.315/(0.315+5.985)}}} = 0.05.    ! Correct !
</pre>

Solved.


------------------


For introductory lessons covering various types of mixture word problems see

&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/Typical-word-problems-on-mixtures-from-the-archive.lesson>Typical word problems on mixtures from the archive</A>

in this site.


You will find there ALL TYPICAL mixture problems with different methods of solutions,
explained at different levels of detalization, &nbsp;from very detailed to very short.


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


Also, &nbsp;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>".



Save the link to this online textbook together with its description


Free of charge online textbook in ALGEBRA-I
https://www.algebra.com/algebra/homework/quadratic/lessons/ALGEBRA-I-YOUR-ONLINE-TEXTBOOK.lesson


to your archive and use it when it is needed.