Moderate -0.5 Part (a) is a standard activity network drawing exercise requiring careful application of precedence rules and dummy placement—routine D1 content. Part (b) requires logical reasoning about critical paths given that D is critical, but this is straightforward once the network is drawn: if D is critical, then B (predecessor) and E (successor) must also be critical, along with the path to completion. This is a typical textbook-style question testing understanding rather than problem-solving insight.
Draw the activity network described in the precedence table above, using activity on arc. Your activity network must contain only the minimum number of dummies.
(5)
Given that D is a critical activity,
state which other activities must also be critical.
(1)
In (a) condone lack of, or incorrect, numbered events throughout. 'Dealt with correctly' means that the activity starts from the correct event but need not necessarily finishes at the correct event, e.g. 'G dealt with correctly' requires the correct precedences for this activity, i.e. B and C labelled correctly and leading into the same node and G starting from that node but do not consider the end node for G. Activity on node is M0.
If an arc is not labelled, for example, if the arc for activity G is not labelled (but the arc is present) then this will lose the second A mark and the final CSO A mark – they can still earn the third A mark – they can still earn the third A mark – they can still earn a fifth A mark if on the top. If two or more arcs are not labelled then mark according to the scheme. Assume that a solid line is an activity which has not been labelled rather than a dummy (even if in the correct place for where a dummy should be).
Ignore incorrect or lack of arrows on the activities for the first four marks only.
- a1M1: At least eight activities (labelled on arc), one start, at least two dummies placed and A, B, and C dealt with correctly.
- a1A1: Activities D, E and 1st dummy (including correct arrow on this dummy – the one after B) dealt with correctly.
- a2A1: Activities F, G and 2nd and 3rd dummies (including correct arrows on these dummies) dealt with correctly.
- a3A1: Activities H, I, J and K dealt with correctly.
- a4A1: CSO (all four previous marks must have been awarded) – all arrows present and correctly placed with one finish no additional dummies. Please check all arcs carefully for arrows.
Note that additional but unnecessary 'correct' dummies that still maintain precedence for the network should only be penalised with the final A mark if earned.
- b1B1: CAO (with no additional activities – so accept B, E, H, K or B, D, E, H, K only).
| Answer/Working | Marks | Guidance |
|---|---|---|
| [Activity on node diagram] | M1 | |
| | A1 | |
| | A1 | |
| | A1 | |
| | A1 | (5) |
| **Activities B, (D), E and K must be critical** | B1 | (1) |
| | **6 marks** | |
**Notes for Question 5:**
In (a) condone lack of, or incorrect, numbered events throughout. 'Dealt with correctly' means that the activity starts from the correct event but need not necessarily finishes at the correct event, e.g. 'G dealt with correctly' requires the correct precedences for this activity, i.e. B and C labelled correctly and leading into the same node and G starting from that node but do not consider the end node for G. **Activity on node is M0**.
**If an arc is not labelled**, for example, if the arc for activity G is not labelled (but the arc is present) then this will lose the second A mark and the final CSO A mark – they can still earn the third A mark – they can still earn the third A mark – they can still earn a fifth A mark if on the top. If two or more arcs are not labelled then mark according to the scheme. Assume that a solid line is an activity which has not been labelled rather than a dummy (even if in the correct place for where a dummy should be).
**Ignore incorrect or lack of arrows on the activities for the first four marks only**.
- **a1M1**: At least eight activities (labelled on arc), one start, at least two dummies placed and A, B, and C dealt with correctly.
- **a1A1**: Activities D, E and 1st dummy (including correct arrow on this dummy – the one after B) dealt with correctly.
- **a2A1**: Activities F, G and 2nd and 3rd dummies (including correct arrows on these dummies) dealt with correctly.
- **a3A1**: Activities H, I, J and K dealt with correctly.
- **a4A1**: CSO (all four previous marks must have been awarded) – **all arrows present and correctly placed** with one finish no additional dummies. **Please check all arcs carefully for arrows**.
**Note that additional but unnecessary 'correct' dummies** that still maintain precedence for the network should only be penalised with the final A mark if earned.
- **b1B1**: CAO (with no additional activities – so accept B, E, H, K or B, D, E, H, K only).
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5.
\begin{center}
\begin{tabular}{|l|l|}
\hline
Activity & Immediately preceding activities \\
\hline
A & - \\
\hline
B & - \\
\hline
C & - \\
\hline
D & B \\
\hline
E & A, D \\
\hline
F & B \\
\hline
G & B, C \\
\hline
H & E, F, G \\
\hline
I & F, G \\
\hline
J & G \\
\hline
K & H, I \\
\hline
\end{tabular}
\end{center}
\begin{enumerate}[label=(\alph*)]
\item Draw the activity network described in the precedence table above, using activity on arc. Your activity network must contain only the minimum number of dummies.\\
(5)
Given that D is a critical activity,
\item state which other activities must also be critical.\\
(1)
\end{enumerate}
\hfill \mbox{\textit{Edexcel D1 2019 Q5 [6]}}