Edexcel D1 2017 January — Question 3 7 marks

Exam BoardEdexcel
ModuleD1 (Decision Mathematics 1)
Year2017
SessionJanuary
Marks7
PaperDownload PDF ↗
Mark schemeDownload PDF ↗
TopicMatchings and Allocation
TypeMaximum matching algorithm application
DifficultyModerate -0.5 This is a standard application of the maximum matching algorithm from D1, requiring students to follow a well-defined procedure to find alternating paths and improve matchings. While it involves multiple parts and careful bookkeeping, it's a routine algorithmic question with no novel problem-solving required—students who have practiced this algorithm will find it straightforward, making it slightly easier than average.
Spec7.02j Isomorphism: of graphs, degree sequences7.02r Graph modelling: model and solve problems using graphs

3. \begin{figure}[h]
\includegraphics[alt={},max width=\textwidth]{8c9bce2c-4156-4bf6-8d02-9e01d6f11948-04_608_511_242_358} \captionsetup{labelformat=empty} \caption{Figure 1}
\end{figure} \begin{figure}[h]
\includegraphics[alt={},max width=\textwidth]{8c9bce2c-4156-4bf6-8d02-9e01d6f11948-04_611_510_242_1201} \captionsetup{labelformat=empty} \caption{Figure 2}
\end{figure} Figure 1 shows the possible allocations of six workers, \(\mathrm { A } , \mathrm { B } , \mathrm { C } , \mathrm { D } , \mathrm { E }\) and F , to six tasks, \(1,2,3\), 4, 5 and 6. Each task must be assigned to only one worker and each worker must be assigned to exactly one task. Figure 2 shows an initial matching.
  1. Starting from the given initial matching, use the maximum matching algorithm to find an alternating path from A to 4 . Hence find an improved matching. You should list the alternating path you use, and state your improved matching.
  2. Explain why it is not possible to find a complete matching. After training, task 1 is added to worker A's possible allocations.
  3. Starting from the improved matching found in (a), use the maximum matching algorithm to find a complete matching. You should list the alternating path you use, and state your complete matching.
    (3)

3.

\begin{figure}[h]
\begin{center}
  \includegraphics[alt={},max width=\textwidth]{8c9bce2c-4156-4bf6-8d02-9e01d6f11948-04_608_511_242_358}
\captionsetup{labelformat=empty}
\caption{Figure 1}
\end{center}
\end{figure}

\begin{figure}[h]
\begin{center}
  \includegraphics[alt={},max width=\textwidth]{8c9bce2c-4156-4bf6-8d02-9e01d6f11948-04_611_510_242_1201}
\captionsetup{labelformat=empty}
\caption{Figure 2}
\end{center}
\end{figure}

Figure 1 shows the possible allocations of six workers, $\mathrm { A } , \mathrm { B } , \mathrm { C } , \mathrm { D } , \mathrm { E }$ and F , to six tasks, $1,2,3$, 4, 5 and 6. Each task must be assigned to only one worker and each worker must be assigned to exactly one task.

Figure 2 shows an initial matching.
\begin{enumerate}[label=(\alph*)]
\item Starting from the given initial matching, use the maximum matching algorithm to find an alternating path from A to 4 . Hence find an improved matching. You should list the alternating path you use, and state your improved matching.
\item Explain why it is not possible to find a complete matching.

After training, task 1 is added to worker A's possible allocations.
\item Starting from the improved matching found in (a), use the maximum matching algorithm to find a complete matching. You should list the alternating path you use, and state your complete matching.\\
(3)
\end{enumerate}

\hfill \mbox{\textit{Edexcel D1 2017 Q3 [7]}}