Question 1099897
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There is entire bunch of lessons in this site on joint work problems:

&nbsp;&nbsp;&nbsp;&nbsp;- <A HREF=http://www.algebra.com/algebra/homework/Rate-of-work-word-problems/Word-problems-WORKING-TOGETHER-by-Fractions.lesson>Using Fractions to solve word problems on joint work</A> 

&nbsp;&nbsp;&nbsp;&nbsp;- <A HREF=http://www.algebra.com/algebra/homework/Rate-of-work-word-problems/Solving-more-complicated-word-problems-on-joint-work.lesson>Solving more complicated word problems on joint work</A> 

&nbsp;&nbsp;&nbsp;&nbsp;- <A HREF=http://www.algebra.com/algebra/homework/Rate-of-work-word-problems/Using-quadr-eqns-to-solve-word-problems-on-joint-work.lesson>Using quadratic equations to solve word problems on joint work</A> 

&nbsp;&nbsp;&nbsp;&nbsp;- <A HREF=http://www.algebra.com/algebra/homework/Rate-of-work-word-problems/Solving-rate-of-work-problem-by-reducing-to-a-system-of-linear-equations.lesson>Solving rate of work problem by reducing to a system of linear equations</A> 

&nbsp;&nbsp;&nbsp;&nbsp;- <A HREF=https://www.algebra.com/algebra/homework/Rate-of-work-word-problems/Selected-problems-from-the-archive-on-joint-work-word-problems.lesson>Selected joint-work word problems from the archive</A> 

&nbsp;&nbsp;&nbsp;&nbsp;- <A HREF=https://www.algebra.com/algebra/homework/Rate-of-work-word-problems/Joint-work-word-problems-for-3-4-5-participants.lesson>Joint-work problems for 3 participants</A>

&nbsp;&nbsp;&nbsp;&nbsp;- <A HREF=https://www.algebra.com/algebra/homework/Rate-of-work-word-problems/Had-the-number-of-workers-be-more-the-job-would-be-completed-sooner.lesson>Had there were more workers, the job would be completed sooner</A>

&nbsp;&nbsp;&nbsp;&nbsp;- <A HREF=https://www.algebra.com/algebra/homework/Rate-of-work-word-problems/One-unusual-joint-work-problem.lesson>One unusual joint work problem</A>

&nbsp;&nbsp;&nbsp;&nbsp;- <A HREF=https://www.algebra.com/algebra/homework/Rate-of-work-word-problems/Special-joint-wok-problems-that-admit-and-require-an-alternative-solution-method.lesson>Special joint work problems that admit and require an alternative solution method</A>

&nbsp;&nbsp;&nbsp;&nbsp;- <A HREF=https://www.algebra.com/algebra/homework/Rate-of-work-word-problems/Joint-work-word-problem-for-the-day-of-April-first.lesson>Joint work word problem for the day of April, 1</A>

&nbsp;&nbsp;&nbsp;&nbsp;- <A HREF=http://www.algebra.com/algebra/homework/Rate-of-work-word-problems/OVERVIEW-of-lessons-on-rate-of-work-problems.lesson>OVERVIEW of lessons on rate-of-work problems</A> 


Read them and get be trained (and get be an expert) in solving joint-work 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 under the topic 
"<U>Rate of work and joint work problems</U>" &nbsp;of the section &nbsp;"<U>Word 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.



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Regarding the given problem in the post, the solution is THIS:


<pre>
The rate of work of two computers working together is  {{{1/10}}} of the job per minute.


The rate of work of the slower computer is {{{1/30}}} of the job per hour.


Hence, the rate of work of the faster computer is the difference  {{{1/10}}} - {{{1/30}}} = {{{3/30 - 1/30}}} = {{{2/30}}} = {{{1/15}}} of the job per hour.


It means that the faster computer can complete the job in 15 minutes working alone.
</pre>

Solved.

 <pre> 
     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.
</pre>

Completely self-evident facts.