<PRE><B>Question 1143495</B>
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&lt;pre&gt;
The rate of work of two computers working together is  {{{1/4}}}  of the job per minute.


The rate of work of the slower computer is  {{{1/9}}}  of the job per minute.


Hence, the rate of work of the faster computer is the difference  {{{1/4}}} - {{{1/9}}} = {{{9/36 - 4/36}}} = {{{5/36}}}  of the job per minute.


It means that the faster computer can complete the job in {{{36/5}}} minutes = 7 minutes and 12 seconds working alone.     &lt;U&gt;ANSWER&lt;/U&gt; 
&lt;/pre&gt;

Solved.

 &lt;pre&gt; 
     When solving problems like this one, you should know and should remember two basic facts:

         - the rate of work of two workers/machines/tubes  is the sum of the rates of individuals;

         - If you are given the combined rate of work of two workers/machines/tubes and the rate of work of one individual, 
           then the rate of work of the other individual is the difference of rates.
&lt;/pre&gt;

Completely self-evident facts.


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It is a standard and typical joint work problem.


There is a wide variety of similar solved joint-work problems with detailed explanations in this site. &amp;nbsp;See the lessons

&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;- &lt;A HREF=http://www.algebra.com/algebra/homework/Rate-of-work-word-problems/Word-problems-WORKING-TOGETHER-by-Fractions.lesson&gt;Using Fractions to solve word problems on joint work&lt;/A&gt; 

&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;- &lt;A HREF=http://www.algebra.com/algebra/homework/Rate-of-work-word-problems/Solving-more-complicated-word-problems-on-joint-work.lesson&gt;Solving more complicated word problems on joint work&lt;/A&gt; 

&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;- &lt;A HREF=https://www.algebra.com/algebra/homework/Rate-of-work-word-problems/Selected-problems-from-the-archive-on-joint-work-word-problems.lesson&gt;Selected joint-work word problems from the archive&lt;/A&gt; 



Read them and get be trained in solving joint-work problems.


Also, &amp;nbsp;you have this free of charge online textbook in ALGEBRA-I in this site

&amp;nbsp;&amp;nbsp;&amp;nbsp;&amp;nbsp;- &lt;A HREF=https://www.algebra.com/algebra/homework/quadratic/lessons/ALGEBRA-I-YOUR-ONLINE-TEXTBOOK.lesson&gt;ALGEBRA-I - YOUR ONLINE TEXTBOOK&lt;/A&gt;.


The referred lessons are the part of this textbook under the topic 
&quot;&lt;U&gt;Rate of work and joint work problems&lt;/U&gt;&quot; &amp;nbsp;of the section &amp;nbsp;&quot;&lt;U&gt;Word problems&lt;/U&gt;&quot;.



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.


</PRE>