AQA D2 2011 June — Question 5

Exam BoardAQA
ModuleD2 (Decision Mathematics 2)
Year2011
SessionJune
TopicNetwork Flows

5 The network shows the evacuation routes along corridors in a college, from two teaching areas to the exit, in case of a fire alarm sounding.
\includegraphics[max width=\textwidth, alt={}, center]{1aca4e91-d1b3-4a78-8880-e42a4fbf3ddb-14_729_1013_434_497} The two teaching areas are at \(A\) and \(G\) and the exit is at \(X\). The number on each edge represents the maximum number of people that can travel along a particular corridor in one minute.
  1. Find the value of the cut shown on the diagram.
  2. Find the maximum flow along each of the routes \(A B D X , G F B X\) and \(G H E X\) and enter their values in the table on Figure 3 opposite.
    1. Taking your answers to part (b) as the initial flow, use the labelling procedure on Figure 3 to find the maximum flow through the network. You should indicate any flow augmenting routes in the table and modify the potential increases and decreases of the flow on the network.
    2. State the value of the maximum flow, and, on Figure 4, illustrate a possible flow along each edge corresponding to this maximum flow.
  3. During one particular fire drill, there is an obstruction allowing no more than 45 people per minute to pass through vertex \(B\). State the maximum number of people that can move through the network per minute during this fire drill. \begin{figure}[h]
    \captionsetup{labelformat=empty} \caption{Figure 3} \includegraphics[alt={},max width=\textwidth]{1aca4e91-d1b3-4a78-8880-e42a4fbf3ddb-15_905_1559_331_292}
    \end{figure} Figure 4
    \includegraphics[max width=\textwidth, alt={}, center]{1aca4e91-d1b3-4a78-8880-e42a4fbf3ddb-15_689_851_1370_598} Maximum flow is \(\_\_\_\_\) people per minute.