If the scheduled completion time for a particular project is 15 days and its earliest expected time is 10 days, then the slack time for the project is
- A+ 25 days
- B+ 5 daysCorrect
- C– 5 days
- D– 25 days
Solution
Concept
Slack time is the extra time available for an event. It is the difference between scheduled completion time (or latest allowable time) and earliest expected time.
Formula
Slack (S) = Ts - TE
Step-by-step solution
1. Identify the given values: Scheduled completion time, Ts = 15 days. Earliest expected time, TE = 10 days. 2. Calculate the slack time using the formula: Slack = Ts - TE Slack = 15 - 10 = + 5 days. Answer: (B) + 5 days
Explanation
Slack time shows how much an event can be delayed without delaying the overall project. When the scheduled time is greater than the earliest expected time, slack is positive. Here, 15 days minus 10 days gives + 5 days.
Why the other options are wrong
A: This is obtained by adding the two times (15 + 10 = 25) instead of subtracting. C: This is obtained by doing (TE - Ts), which reverses the standard formula for slack. D: This is obtained by taking the negative sum of both values.
Shortcut
Slack = Scheduled time - Earliest time = 15 - 10 = +5 days.
Common mistake
Students sometimes subtract scheduled time from earliest time (10 - 15 = -5) and choose the negative value by mistake.
Correct answer: B) + 5 days