GATE 2025 ME – Question 65
A project involves eight activities with the precedence relationship and duration as shown in the table below. The slack for the activity D is _____ hours (answer in integer).
| Activity | Immediate predecessor | Duration (hours) |
|---|---|---|
| A | - | 4 |
| B | A | 8 |
| C | A | 5 |
| D | B | 2 |
| E | B | 7 |
| F | C | 6 |
| G | D | 3 |
| H | E, F, G | 9 |
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Correct answer: 2
Explanation
The earliest finish times are A: 4, B: 12, C: 9, D: 14, E: 19, F: 15, G: 17 and H: 28. The project length is 28 hours. Going backwards, H must start at 19, so G must finish by 19 and start by 16, so D must finish by 16 and start by 14. D can start as early as 12, so its slack is $14 - 12 = 2$ hours.