Question 889065
One job can be done  in d days by d men in the group. if the number of men is reduced by 4, the job will be delayed by 5 days. How many men were there originally in the group?


Reducing the number of men to d-4 makes the 1 job require d+5 days.


The d men in d days did one job.  The reduced men, more days arrangement was also for one job.  The number of jobs is equal.


RT=J for rate, time, job.  We can use r for the one-man work rate.


{{{highlight_green(d*r*d=1=(d-4)r(d+5))}}}.
The factor of r occurs on both sides of the equation, and the only other variable resulting in terms in powers of one and two is d.  Solve for d.