Question 1048767
SEE THE METHOD FURTHER DOWN THE PAGE FOR A GOOD WAY  *


r+2r=1/20 because the sum of the individual rates of the two printers working together is their rate working together.  "1" is for "one job of THE flyers", and r is the rate of the slower printer, unknown but can find it.


{{{3r=1/20}}}
{{{r=1/60}}}


The faster printer would do the job in 60 minutes.  
The slower printer would need 120 minutes.


Did that make sense?  (SEE THE METHOD BELOW!)





*  This method will seem to have less chance for mistakes:
Let x be time for the fast printer to do one job.
This means, 2x is how long for the slow printer to do the same job.
{{{1/x+1/(2x)=1/20}}} for one job in 20 minutes for the two printers joined in the task.


{{{2/(2x)+1/(2x)=1/20}}}
{{{3/(2x)=1/20}}}
{{{2x/3=20}}}
{{{x=(3/2)20}}}
{{{highlight(x=30)}}}


The fast printer would need 30 minutes alone to do 1 job.
The slow printer would need 60 minutes alone to do the same 1 job.