Edexcel D1 2014 June — Question 2 7 marks

Exam BoardEdexcel
ModuleD1 (Decision Mathematics 1)
Year2014
SessionJune
Marks7
PaperDownload PDF ↗
Mark schemeDownload PDF ↗
TopicMatchings and Allocation
TypeExplain why complete matching impossible
DifficultyModerate -0.8 This is a standard D1 bipartite matching question requiring application of Hall's Marriage Theorem to identify why complete matching fails, then straightforward application of the alternating path algorithm. The concepts are algorithmic rather than requiring mathematical insight, and the question guides students through each step explicitly.
Spec7.02a Graphs: vertices (nodes) and arcs (edges)7.02b Graph terminology: tree, simple, connected, simply connected7.02c Graph terminology: walk, trail, path, cycle, route

2. \begin{figure}[h]
\includegraphics[alt={},max width=\textwidth]{23cc3c59-35d8-4120-9965-952c0ced5b3d-3_437_399_251_511} \captionsetup{labelformat=empty} \caption{Figure 1}
\end{figure} \begin{figure}[h]
\includegraphics[alt={},max width=\textwidth]{23cc3c59-35d8-4120-9965-952c0ced5b3d-3_437_401_251_1151} \captionsetup{labelformat=empty} \caption{Figure 2}
\end{figure} Figure 1 shows the possible allocations of five employees, Ali (A), Campbell (C), Hugo (H), Janelle (J) and Polly (P), to five tasks 1, 2, 3, 4 and 5.
  1. Explain why it is not possible to find a complete matching. It is decided that one of the employees should be trained so that a complete matching becomes possible. There are only enough funds for one employee to be trained. Two employees volunteer to undergo training. Janelle can be trained to do task 1 or Hugo can be trained to do task 5.
  2. Decide which employee, Janelle or Hugo, should undergo training. Give a reason for your answer. You may now assume that the employee you identified in (b) has successfully undergone training. Figure 2 shows an initial matching.
  3. Starting from the given initial matching, use the maximum matching algorithm to find a complete matching. You should list the alternating path that you use, and state the complete matching.

2.

\begin{figure}[h]
\begin{center}
  \includegraphics[alt={},max width=\textwidth]{23cc3c59-35d8-4120-9965-952c0ced5b3d-3_437_399_251_511}
\captionsetup{labelformat=empty}
\caption{Figure 1}
\end{center}
\end{figure}

\begin{figure}[h]
\begin{center}
  \includegraphics[alt={},max width=\textwidth]{23cc3c59-35d8-4120-9965-952c0ced5b3d-3_437_401_251_1151}
\captionsetup{labelformat=empty}
\caption{Figure 2}
\end{center}
\end{figure}

Figure 1 shows the possible allocations of five employees, Ali (A), Campbell (C), Hugo (H), Janelle (J) and Polly (P), to five tasks 1, 2, 3, 4 and 5.
\begin{enumerate}[label=(\alph*)]
\item Explain why it is not possible to find a complete matching.

It is decided that one of the employees should be trained so that a complete matching becomes possible. There are only enough funds for one employee to be trained.

Two employees volunteer to undergo training. Janelle can be trained to do task 1 or Hugo can be trained to do task 5.
\item Decide which employee, Janelle or Hugo, should undergo training. Give a reason for your answer.

You may now assume that the employee you identified in (b) has successfully undergone training.

Figure 2 shows an initial matching.
\item Starting from the given initial matching, use the maximum matching algorithm to find a complete matching. You should list the alternating path that you use, and state the complete matching.
\end{enumerate}

\hfill \mbox{\textit{Edexcel D1 2014 Q2 [7]}}