Question 15

Explanation

We will use the concept of inverse proportion to determine the total number of workers needed, then calculate the difference with the initial number of workers.

Calculating Total Workload

The total project workload is constant, which is:

Calculating Required Number of Workers

If the completion time is accelerated to 40 days, the number of workers required ($P$) is:

Calculating Additional Workers

The existing number of workers is 80. Thus, the additional workers needed are:

So, the number of additional workers needed is 20 people.