| Exam Board | Edexcel |
|---|---|
| Module | D2 (Decision Mathematics 2) |
| Session | Specimen |
| Marks | 11 |
| Paper | Download PDF ↗ |
| Mark scheme | Download PDF ↗ |
| Topic | Network Flows |
| Type | Transportation problem: north-west corner |
| Difficulty | Moderate -0.5 This is a standard algorithmic application of the north-west corner method and stepping-stone algorithm from Decision Mathematics. While it requires careful bookkeeping across multiple steps, it follows a mechanical procedure with no conceptual insight or problem-solving required—students simply apply learned algorithms to given data. |
| Spec | 7.06a LP formulation: variables, constraints, objective function7.06d Graphical solution: feasible region, two variables |
| \cline { 2 - 5 } \multicolumn{1}{c|}{} | \(D\) | \(E\) | \(F\) | Available |
| \(A\) | 21 | 24 | 16 | 24 |
| \(B\) | 18 | 23 | 17 | 32 |
| \(C\) | 15 | 19 | 25 | 14 |
| Required | 20 | 30 | 20 | |
| \cline { 1 - 4 } | ||||
| \cline { 1 - 4 } |
3. Freezy Co. has three factories $A , B$ and $C$. It supplies freezers to three shops $D , E$ and $F$. The table shows the transportation cost in pounds of moving one freezer from each factory to each outlet. It also shows the number of freezers available for delivery at each factory and the number of freezers required at each shop. The total number of freezers required is equal to the total number of freezers available.
\begin{center}
\begin{tabular}{ | c | c | c | c | c | }
\cline { 2 - 5 }
\multicolumn{1}{c|}{} & $D$ & $E$ & $F$ & Available \\
\hline
$A$ & 21 & 24 & 16 & 24 \\
\hline
$B$ & 18 & 23 & 17 & 32 \\
\hline
$C$ & 15 & 19 & 25 & 14 \\
\hline
Required & 20 & 30 & 20 & \multicolumn{1}{|c}{} \\
\cline { 1 - 4 }
& & & & \\
\cline { 1 - 4 }
\end{tabular}
\end{center}
\begin{enumerate}[label=(\alph*)]
\item Use the north-west corner rule to find an initial solution.
\item Obtain improvement indices for each unused route.
\item Use the stepping-stone method once to obtain a better solution and state its cost.
\end{enumerate}
\hfill \mbox{\textit{Edexcel D2 Q3 [11]}}