D1 June 2018 Q3
3.
| Activity | Immediately preceding activities |
|---|---|
| A | – |
| B | – |
| C | – |
| D | A |
| E | D |
| F | A, B |
| G | A, B, C |
| H | A, B, C |
| I | E, F, G |
| J | E, F, G |
| K | E, F, G, H |
Given that D is a critical activity,
| Scheme | Marks |
|---|---|
| M1 (7 activities, 1 start + 2 dummies) | |
| A1 (ABCD+1st 2 dummies) | |
| A1 (EFGH) | |
| A1 (IJK+3 dummy) | |
| A1 (CSO) | |
| (5) |
Notes
Condone lack of, or incorrect, numbered events throughout. ‘Dealt with correctly’ means that the activity starts from the correct event but need not necessarily finish at the correct event, e.g. ‘G dealt with correctly’ requires the correct precedences for this activity, i.e. A, B and C labelled correctly and leading into the same node and G starting from that node but do not consider the end event for G. Activity on node is M0. Note that additional/unnecessary dummies that do not break the precedence condition can earn the first three A marks but will lose the final A mark (the CSO mark). However, additional unlabelled activities will lose the corresponding A marks if they effect the ‘dealt with correctly’ condition for other activities
If an activity, say C is not labelled (but the arc is present) then this will lose the first A mark and the final (CSO) A mark – they can still earn the second and third A marks on the bod.
Ignore lack of arrows on the activities for the first four marks only. If no arrows on any dummies then maximum mark in (a) is M1 onlya1M1: Seven activities (labelled on arc), one start and at least two dummies placed
a1A1: Activities A, B, C, 1st two dummies (including arrows on these two dummies) and D dealt with correctly. The first two dummies are those at the end of activities A and B
a2A1: Activities E, F, G and H dealt with correctly
a3A1: 3rd dummy (including arrow on this dummy at the end of activity F) and activities I, J and K dealt with correctly
a4A1: CSO (all previous marks must have been awarded) – final dummy correctly placed (+arrow), all arrows present, exactly four dummies correctly placed with one finish. Please check all arcs carefully for arrows
Note additional valid solutions:- the arrow on the final dummy between I and J reversed so that activity I will now end at the finish node
- Activities I and J interchanged
- A combination of both points above (i.e. I and J interchanged and the arrow on the dummy reversed)
Therefore it is vital that the diagram is checked carefully for these other equally acceptable/valid solutions
| Scheme | Marks |
|---|---|
| Given that D is critical this implies that A and E are guaranteed to be critical | M1 A1 |
| (2) | |
| (7 marks) |
Notes
b1M1: One correct activity with at most 4 activities stated (ignore any mention of D in this part)
b1A1: Both (A and E) correct and no others