Question 1033132
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A chemistry experiment requires that a vacuum be created in a chamber. A small vacuum pump requires 15 seconds to evacuate the chamber. 
Working together, the chamber can be evacuated in 4 sec. 
Find the time required for the larger vacuum pump working alone to evacuate the chamber.
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The set up is like this:
{{{t/A + t/B = 1}}}
where A and B are the times working alone and t is the time working together...thus we have
{{{t/15 + t/4 = 1}}}
Multiply by 60 and get
{{{4t + 15t = 60}}}
{{{19t = 60}}}
and
{{{t = 60/19}}} = {{{3}}}{{{3/19}}} seconds.


<U>Answer</U>.  {{{3}}}{{{3/19}}} seconds.


There are many other similar solved joint-work problems in the lessons

&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=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> 

in this site.


It is good material for you to learn and to get trained in solution of joint-work problems.