Question 973750
RT=J rate time job.  


Let r be work rate for one worker or man.
Let n be the number of additional men needed for the remaining expected days.
{{{system((45r)350=4&1/2,((n+45)r)(350-200)=(12-4&1/2))}}}


The first rate equation was an expectation or estimate which fell short of the 12 km length of the job.  This equation gives the one-man work rate in kilometers per day.  This value for r will be used in the second equation for finding the number of additional n men required for completing the remaining length of bridge, twelve minus four and a half kilometers of bridge, in the required or earlier estimated 350 days.  Since 200 days were used and the bridge not yet finished, the contractor wants to be able to finish the unbuilt bridge within 150 days after the first 200 days.


Examine the system's equations carefully to understand that they are in the uniform rates form, RT=J.