Question 4220
If you can do a job in 6 hours, then in 1 hour you can do {{{1/6}}} of the job.  
If your friend can do the same job in 3 hours, then in 1 hour he/she can do {{{1/3}}} of the job.  
Let x = the time it would take you to do the job working together.  
Then in 1 hour, together you could do 1/x of the job.


So, the equation is that what you can do in 1 hour, plus what your friend can do in 1 hour, equals what you can do together in 1 hour, or as follows:
{{{1/6 + 1/3 = 1/x}}}


This equation can be solved in two ways.  For those who do NOT like fractions, you can multiply both sides of the equation by the Least Common Denominator (LCD), which in the case is 6x:
{{{6x * (1/6) + 6x * (1/3) = 6x * (1/x)}}}


Reduce all the fractions, which eliminates all the denominators:
{{{x + 2x = 6}}}
{{{3x = 6}}}
{{{x = 2 hrs}}}


R^2 at SCC