Edexcel D1 2011 January — Question 5 11 marks

Exam BoardEdexcel
ModuleD1 (Decision Mathematics 1)
Year2011
SessionJanuary
Marks11
PaperDownload PDF ↗
Mark schemeDownload PDF ↗
TopicRoute Inspection
TypeChinese Postman with flexible endpoints
DifficultyStandard +0.3 This is a standard Chinese Postman problem with a straightforward extension. Part (a) is routine application of the algorithm (identify odd vertices, find minimum pairings). Part (b) requires stating the solution. Part (c) adds a twist with flexible endpoints, but the reasoning is accessible: remove the longest edge between D and the optimal finishing vertex from the repeated edges. While multi-part, each step follows a well-defined algorithm with no novel insight required, making it slightly easier than average.
Spec7.04e Route inspection: Chinese postman, pairing odd nodes

5. \begin{figure}[h]
\includegraphics[alt={},max width=\textwidth]{0360f78d-e18c-4c47-a2ec-ddd705a4175f-6_867_1381_260_342} \captionsetup{labelformat=empty} \caption{Figure 5}
\end{figure} [The total weight of the network is 31.6 km ]
Figure 5 models a network of roads. The road markings on these roads are to be renewed. The number on each arc represents the length, in km , of that road. In order to renew the road markings, each road must be traversed at least once.
  1. Use the route inspection algorithm, starting and finishing at A , to find a suitable route, which should be stated. You must make your method and working clear.
  2. State the roads that must be traversed twice and the length of the route.
    (3) The machine that will be used to renew the road markings can only be delivered to D . It will start at D, but it may finish at any vertex.
    Each road must still be traversed at least once.
  3. Given that the route is to be minimised, determine where the machine should finish. Give reasons to justify your answer.
    (3)

5.

\begin{figure}[h]
\begin{center}
  \includegraphics[alt={},max width=\textwidth]{0360f78d-e18c-4c47-a2ec-ddd705a4175f-6_867_1381_260_342}
\captionsetup{labelformat=empty}
\caption{Figure 5}
\end{center}
\end{figure}

[The total weight of the network is 31.6 km ]\\
Figure 5 models a network of roads. The road markings on these roads are to be renewed. The number on each arc represents the length, in km , of that road. In order to renew the road markings, each road must be traversed at least once.
\begin{enumerate}[label=(\alph*)]
\item Use the route inspection algorithm, starting and finishing at A , to find a suitable route, which should be stated. You must make your method and working clear.
\item State the roads that must be traversed twice and the length of the route.\\
(3)

The machine that will be used to renew the road markings can only be delivered to D . It will start at D, but it may finish at any vertex.\\
Each road must still be traversed at least once.
\item Given that the route is to be minimised, determine where the machine should finish. Give reasons to justify your answer.\\
(3)
\end{enumerate}

\hfill \mbox{\textit{Edexcel D1 2011 Q5 [11]}}