| Exam Board | Edexcel |
|---|---|
| Module | D1 (Decision Mathematics 1) |
| Year | 2018 |
| Session | January |
| Marks | 8 |
| Paper | Download PDF ↗ |
| Mark scheme | Download PDF ↗ |
| Topic | Critical Path Analysis |
| Type | Draw activity network from table |
| Difficulty | Easy -1.2 Drawing an activity network from a precedence table is a standard, routine D1 task requiring only direct application of learned rules about nodes, arcs, and dummy activities. It involves minimal problem-solving—students follow an algorithmic procedure to translate the table into the network diagram. |
| Spec | 7.06a LP formulation: variables, constraints, objective function |
| Answer | Marks | Guidance |
|---|---|---|
| Answer | Mark | Guidance |
| Network diagram with correct structure | M1 | At least nine activities (labelled on arc), one start, at least two dummies placed and A, B, C, D dealt with correctly |
| E, F and 1st dummy + correct arrow | A1 | (the dummy after B) dealt with correctly |
| G, H and I dealt with correctly | A1 | |
| J, K and 2nd dummy + correct arrow | A1 | (the dummy after E) dealt with correctly |
| CSO – all arrows present and correctly placed, one finish, no additional dummies | A1 (5) | Please check all arcs carefully for arrows |
| Answer | Marks | Guidance |
|---|---|---|
| Answer | Mark | Guidance |
| \(25 - 12 - 10 = 3\) | B1 (1) | CAO (accept 3 with no working) |
| Answer | Marks | Guidance |
|---|---|---|
| Answer | Mark | Guidance |
| The path is not critical as activity H is not critical because this activity has a total float of 3 | M1 A1 (2) | M1: No + attempt at reason; A1: CAO - must mention that the (total) float of H is 3 or float is positive or float is not zero; (b) must be correct; H must be mentioned with numerical argument |
## Question 8:
### Part (a):
| Answer | Mark | Guidance |
|--------|------|----------|
| Network diagram with correct structure | M1 | At least nine activities (labelled on arc), one start, at least two dummies placed and A, B, C, D dealt with correctly |
| E, F and 1st dummy + correct arrow | A1 | (the dummy after B) dealt with correctly |
| G, H and I dealt with correctly | A1 | |
| J, K and 2nd dummy + correct arrow | A1 | (the dummy after E) dealt with correctly |
| CSO – all arrows present and correctly placed, one finish, no additional dummies | A1 **(5)** | Please check all arcs carefully for arrows |
### Part (b):
| Answer | Mark | Guidance |
|--------|------|----------|
| $25 - 12 - 10 = 3$ | B1 **(1)** | CAO (accept 3 with no working) |
### Part (c):
| Answer | Mark | Guidance |
|--------|------|----------|
| The path is not critical as activity H is not critical because this activity has a total float of 3 | M1 A1 **(2)** | M1: No + attempt at reason; A1: CAO - must mention that the (total) float of H is 3 **or** float is positive **or** float is not zero; (b) must be correct; H must be mentioned with numerical argument |8.
\begin{center}
\includegraphics[max width=\textwidth, alt={}]{e0c89aba-9d2e-469b-8635-d513df0b65a4-19_2261_50_315_33}
\end{center}
\begin{figure}[h]
\begin{center}
\includegraphics[alt={},max width=\textwidth]{e0c89aba-9d2e-469b-8635-d513df0b65a4-19_862_1422_196_258}
\captionsetup{labelformat=empty}
\caption{Figure 4}
\end{center}
\end{figure}
4.
\begin{figure}[h]
\begin{center}
\includegraphics[alt={},max width=\textwidth]{e0c89aba-9d2e-469b-8635-d513df0b65a4-20_1196_899_251_529}
\captionsetup{labelformat=empty}
\caption{Figure 5}
\end{center}
\end{figure}
5.
\begin{figure}[h]
\begin{center}
\includegraphics[alt={},max width=\textwidth]{e0c89aba-9d2e-469b-8635-d513df0b65a4-24_871_1536_210_205}
\captionsetup{labelformat=empty}
\caption{Figure 6\\[0pt]
[The total weight of the network is 601]}
\end{center}
\end{figure}
6.\\
$\begin{array} { l l l l l l l l l l } 30 & 11 & 21 & 53 & 50 & 39 & 16 & 4 & 60 & 43 \end{array}$
7.\\
\begin{center}
\includegraphics[max width=\textwidth, alt={}]{e0c89aba-9d2e-469b-8635-d513df0b65a4-32_2636_1825_119_122}
\end{center}
\hfill \mbox{\textit{Edexcel D1 2018 Q8 [8]}}