Question 252693
We are assuming that the other 15 added will work at the same pace/rate as the first 15 which is not always a wise assumption.
in one day 15 men do 1/90 of the job
so 30 men should be able to do 2/90 in the same day or 1/45 of the job in one day
so in 45 days 30 men should be able to finish the job