D1 June 2016 Q2
2. Draw the activity network described in the precedence table below, using activity on arc and exactly three dummies. (5)
| Activity | Immediately preceding activities |
|---|---|
| A | – |
| B | – |
| C | A |
| D | A |
| E | B |
| F | B |
| G | A, E, F |
| H | F |
| I | C |
| J | D, G |
| K | D, G |
| Scheme | Marks |
|---|---|
| M1 (7 activities, 1 start and 2 dummies) | |
| A1 (ABCDEF) | |
| A1 (GH + first two dummies) | |
| A1 (IJK) | |
| A1 CSO | |
| (5 marks) |
Notes
Condone lack of, or incorrect, numbered events throughout and arcs which cross one another. ‘Dealt with correctly’ means that the activity starts from the correct event but need not necessarily finish at the correct event, e.g. ‘J dealt with correctly’ requires the correct precedences for this activity, i.e. D and G labelled correctly and leading into the same node and J starting from that node but not necessarily J leading into the end node. Activity on node is M0
Ignore incorrect or lack of arrows on the activities for the first four marks only
1M1: 7 activities (labelled on arc), one start and two dummies placed
1A1: Activities A, B, C, D, E and F dealt with correctly
2A1: Activities G, H and the first two dummies (including arrows on these two dummies) dealt with correctly. By ‘first two dummies’ these are the ones leading into the event at the end of E
3A1: Activities I, J and K dealt with correctly
4A1: CSO (all four previous marks must have been awarded) – final dummy correctly placed, all arrows present and correctly placed with one finish and no additional dummies. Please check all arcs carefully for arrows
Note that there are a number of additional valid solutions in which the candidate may finish their network diagram which are different (but are equivalent) to the example given above:
e.g.
- the arrow on the final dummy between J and K reversed so that activity H will now end at the finish node
- Activities J and K interchanged
- A combination of both points above (i.e. J and K interchanged and the arrow on the dummy reversed)
- Activity H leading directly into the finish node
Therefore it is vital that the diagram is checked carefully for these other equally acceptable/valid solutions