D1 June 2018 Q6
6.
A project is modelled by the activity network shown in Figure 4. The activities are represented by the arcs. The number in brackets on each arc gives the time, in days, to complete the corresponding activity. Each activity requires one worker. The project is to be completed in the shortest possible time.
| Scheme | Marks |
|---|---|
| M1 | |
| A1 | |
| M1 | |
| A1 | |
| (4) |
Notes
a1M1: All top boxes complete, values in the top boxes generally increasing in the direction of the arrows (‘left to right’), condone one ‘rogue’ value (if values do not increase in the direction of the arrows then if one value is ignored and then the values do increase in the direction of the arrows then this is considered to be only one rogue value)
a1A1: CAO for the top boxes
a2M1: All bottom boxes complete, values generally decreasing in the opposite direction of the arrows (‘right to left’), condone one rogue. Condone missing 0 and/or 35 for the M only
a2A1: CAO for the bottom boxes
| Scheme | Marks |
|---|---|
| Critical activities: A, D, J and N | B1 |
| (1) |
Notes
b1B1: CAO (A, D, J and N)
| Scheme | Marks |
|---|---|
| M1 | |
| A1 | |
| A1 | |
| A1 | |
| (4) |
Notes
c1M1: At least twelve activities including at least six floats. A scheduling diagram only scores M0 – however, if a scheduling diagram appears after a Gantt chart then mark Gantt chart and isw their scheduling
c1A1: The critical activities dealt with correctly and appearing just once (A, D, J and N) and three non-critical activities dealt with correctly
c2A1: Any seven non-critical activities correct (this mark is not dependent on the previous A mark)
c3A1: CSO – completely correct Gantt chart (exactly fourteen activities appearing just once)
| Scheme | Marks |
|---|---|
| Minimum workers is 4 e.g. D, E, F and G | M1 |
| together with \(11 \lt \text{time} \lt 12\) | A1 |
| (2) | |
| (11 marks) |
Notes
d1M1: Either a statement with the correct number of workers (4) and the correct activities (D, E, F and G) with any numerical time stated or the correct number of workers (4) and a correct time
d1A1: A completely correct statement with details of both time and activities. Candidates only need to give a time within the correct interval of \(11 \lt \text{time} \lt 12\). Please note the strict inequalities for the time interval (e.g. implying a time of 11 is incorrect). Answers given as an interval of time are acceptable provided the time interval stated is correct for all its possible values (e.g. ‘time 11 – 12’ is A0, ‘in the interval 11 – 12’ is A0 but ‘betweeen 11 and 12’ is A1). Allow for example, ‘on day 12’ as equivalent to \(11 \lt \text{time} \lt 12\)