Question 286491
1.I takes Jose 6 hours to change the breaks on his car. His wife Betty can do the breaks in 8 hours. How long would it take them if they work together?
<pre><font size = 4 color = "indigo"><b>
Make this chart, putting in 1 for the no of jobs done,
the given times to do the job and the unknown x for 
the quantity that was asked for, namely the time it
would take both together: 


             Number of       Rate in       Time in 
             Jobs Done      Jobs/hour       hours
Jose alone        1                            6
Betty alone       1                            8
both together     1                            x


Now use the formula

{{{Rate_in_Jobs_per_hour = (Number_of_jobs_done)/(Time)}}}

to fill in the three rates:

             Number of       Rate in       Time in 
             Jobs Done      Jobs/hour       hours
Jose alone        1            1/6             6
Betty alone       1            1/8             8
both together     1            1/x             x

Now to set up the equation, we use:

{{{"Jose's_rate"}}}{{{""+""}}}{{{"Betty's_rate"}}}{{{""=""}}}{{{"Rate_together"}}} 

{{{1/6+1/8=1/x}}}

Can you solve that for x?  If not post again asking how.

Answer {{{x=24/7=3&3/7}}} hours.

Edwin</pre>