Five workers have been hired to complete a job. If one additional worker is hired, they could complete the job $8$ days earlier. If the job needs to completed $28$ days earlier, how many additional workers should be hired?
Number of workers * number of days = total job done = number of work units
So....let N be the original number of days and N - 8 = 8 days earlier and we have this equation
5 N = 6 ( N - 8)
5N = 6N - 48
48 = 6N - 5N
48 = N
And the amt of work that the job requires = 5 * 48 = 240 work units
So...if the job could be be completed 28 days earlier we have this equation where W is the number of workers needed
W ( 48 - 28) = 240
W ( 20) = 240
W = 240 / 20 = 12
So.... 12 - 5 = 7 additional workers should be hired to complete the job 28 days earlier