81 equally efficient people could complete a piece of work in 15 days. Initially 45 such people started working together. But after they worked together for 6 days their employer wanted that the work should be completed in a total of 21 days. However any new worker who joins is only as efficient as any of the 45 people already working. How many new workers did the employer hire to work alongside the initial 45 people to meet the deadline?
81 equally efficient people could complete a piece of work in 15 days. Initially 45 such people started working together. But after they worked together for 6 days their employer wanted that the work should be completed in a total of 21 days. However any new worker who joins is only as efficient as any of the 45 people already working. How many new workers did the employer hire to work alongside the initial 45 people to meet the deadline?
Solution
Total work units (1 unit work of one original person in one day).
Work done by people in days units
Remaining work units
The deadline of days includes the first days, so days left
Work needed per day units
The original people do units per day.
Extra work needed per day units
Each new worker is as efficient, so does unit per day.
Number of new workers
Therefore, the employer hired new workers.