40 skilled employees × 60 days × 8 hours/day
= 19,200 man-hours total work
During first 30 days:
40 skilled employees × 30 days × 8 hours/day
= 9,600 man-hours completed
So remaining work:
19,200 − 9,600 = 9,600 man-hours left
30 employees leave.
Remaining skilled employees = 40 − 30 = 10 skilled employees
40 new employees join, but they are 50% as productive.
So each new employee = 0.5 of a skilled employee.
Effective productivity of 40 new employees =
40 × 0.5 = 20 skilled-employee equivalents
10 skilled + 20 equivalent = 30 skilled-employee equivalents
Remaining man-hours = 9,600
Available days = 30
Required man-hours per day:
9,600 ÷ 30 = 320 man-hours/day
320 ÷ 30 = 10.666... hours/day
10.666 hours =
10 hours + 0.666×60 minutes
0.666×60 = 40 minutes
→ 10 hours 40 minutes per day
The extra time per day should the new team work to avoid any delay in the completion of the project = 10 hours 40 minutes - 8 hours = 2 hours 40 minutes