Hard Further Maths Transportation problems Questions
Challenging, exam-style Further Maths Transportation problems questions with worked solutions. Stretch yourself on the hardest transportation, improvement-index, optimality, stepping-stone problems.
The table below shows the cost (in pounds) of transporting one unit from each supply point Si to each demand point Dj, together with the supplies and demands. S1S2S3DemandD13834D24337D385711Supply7105 Starting from the north-west corner solution, perform one stepping-stone iteration and find the resulting total cost.
Show worked solution
Worked solution
Apply the north-west corner rule
allocate min(si,dj) starting at the top-left cell
Each step fills the current top-left cell and crosses out an exhausted supply or demand.
The entering cell gains θ units and the minus cells lose them.
Cost the new allocation
new cost=101+(4)(−2)=93
The cost changes by θ times the entering improvement index.
Recall what a transportation problem asks
mini∑j∑cijxij
The aim is to meet every demand from the available supplies at least total cost.
Recall the balance condition
i∑si=j∑dj
A transportation problem can only be solved once total supply equals total demand.
Recall how a dummy restores balance
dummy supply or demand=i∑si−j∑dj
A dummy row or column with zero costs absorbs the surplus, leaving a balanced problem.
Recall the number of occupied cells needed
occupied cells=m+n−1
A non-degenerate basic feasible solution of an m×n problem fills exactly m+n−1 cells.
Recall the north-west corner rule
start at the top-left cell and allocate as much as possible
Each allocation exhausts a supply or a demand, and we move right or down accordingly.
Recall the shadow-cost equations
ui+vj=cij on every occupied cell
Fixing u1=0 makes the potentials ui and vj uniquely determined.
Recall the improvement index
Iij=cij−ui−vj
The improvement index measures the change in cost from sending one unit through an empty cell.
State the new total cost
new cost=93
This is the cost after one stepping-stone iteration.
Answer
93
Question 2
9 markschallenging
The table below shows the cost (in pounds) of transporting one unit from each supply point Si to each demand point Dj, together with the supplies and demands. S1S2S3DemandD18633D236813D33951Supply647 Use the north-west corner method and the stepping-stone method to find the minimum total transportation cost.
Show worked solution
Worked solution
Apply the north-west corner rule
allocate min(si,dj) starting at the top-left cell
Each step fills the current top-left cell and crosses out an exhausted supply or demand.
Move to a better solution through the entering cell
θ=3 at (S3,D1),I31=−10
The stepping-stone cycle reduces the cost by θ∣Iij∣.
Cost the improved allocation
110+(3)(−10)=80
One iteration is enough here to reach the optimum.
Confirm optimality of the new solution
every improvement index of the new solution≥0
No empty cell can reduce the cost further, so this allocation is optimal.
Recall what a transportation problem asks
mini∑j∑cijxij
The aim is to meet every demand from the available supplies at least total cost.
Recall the balance condition
i∑si=j∑dj
A transportation problem can only be solved once total supply equals total demand.
Recall how a dummy restores balance
dummy supply or demand=i∑si−j∑dj
A dummy row or column with zero costs absorbs the surplus, leaving a balanced problem.
Recall the number of occupied cells needed
occupied cells=m+n−1
A non-degenerate basic feasible solution of an m×n problem fills exactly m+n−1 cells.
Recall the north-west corner rule
start at the top-left cell and allocate as much as possible
Each allocation exhausts a supply or a demand, and we move right or down accordingly.
State the minimum total cost
Cmin=80
This is the least possible total transportation cost.
Answer
80
Question 3
9 markschallenging
The table below shows the cost (in pounds) of transporting one unit from each supply point Si to each demand point Dj, together with the supplies and demands. S1S2S3DemandD14231D294911D37785Supply854 Find the north-west corner solution, compute its improvement indices with u1=0, and state whether it is optimal.
Show worked solution
Worked solution
Apply the north-west corner rule
allocate min(si,dj) starting at the top-left cell
Each step fills the current top-left cell and crosses out an exhausted supply or demand.
The aim is to meet every demand from the available supplies at least total cost.
Recall the balance condition
i∑si=j∑dj
A transportation problem can only be solved once total supply equals total demand.
Recall how a dummy restores balance
dummy supply or demand=i∑si−j∑dj
A dummy row or column with zero costs absorbs the surplus, leaving a balanced problem.
Recall the number of occupied cells needed
occupied cells=m+n−1
A non-degenerate basic feasible solution of an m×n problem fills exactly m+n−1 cells.
Recall the north-west corner rule
start at the top-left cell and allocate as much as possible
Each allocation exhausts a supply or a demand, and we move right or down accordingly.
Recall the shadow-cost equations
ui+vj=cij on every occupied cell
Fixing u1=0 makes the potentials ui and vj uniquely determined.
Recall the improvement index
Iij=cij−ui−vj
The improvement index measures the change in cost from sending one unit through an empty cell.
Recall the optimality test
optimal⟺Iij≥0 for every unoccupied cell
If any improvement index is negative, cost can still be reduced.
Recall the stepping-stone cycle
+−+−around a closed loop
The loop starts at the entering cell and turns only at occupied cells.
Recall how much is shifted round the loop
θ=min{allocations at the minus cells}
Shifting θ keeps every allocation non-negative and empties one cell.
State whether the solution is optimal
not optimal: I13=−5<0
The improvement indices alone decide whether a solution is optimal.
Answer
not optimal: I13=−5<0
Question 4
9 markschallenging
The table below shows the cost (in pounds) of transporting one unit from each supply point Si to each demand point Dj, together with the supplies and demands. S1S2S3DemandD18251D23397D333512Supply974 Find the north-west corner solution and its improvement indices (with u1=0). Which empty cell should enter the solution next?
Show worked solution
Worked solution
Apply the north-west corner rule
allocate min(si,dj) starting at the top-left cell
Each step fills the current top-left cell and crosses out an exhausted supply or demand.
The empty cell with the most negative index enters the solution.
Recall what a transportation problem asks
mini∑j∑cijxij
The aim is to meet every demand from the available supplies at least total cost.
Recall the balance condition
i∑si=j∑dj
A transportation problem can only be solved once total supply equals total demand.
Recall how a dummy restores balance
dummy supply or demand=i∑si−j∑dj
A dummy row or column with zero costs absorbs the surplus, leaving a balanced problem.
Recall the number of occupied cells needed
occupied cells=m+n−1
A non-degenerate basic feasible solution of an m×n problem fills exactly m+n−1 cells.
Recall the north-west corner rule
start at the top-left cell and allocate as much as possible
Each allocation exhausts a supply or a demand, and we move right or down accordingly.
Recall the shadow-cost equations
ui+vj=cij on every occupied cell
Fixing u1=0 makes the potentials ui and vj uniquely determined.
Recall the improvement index
Iij=cij−ui−vj
The improvement index measures the change in cost from sending one unit through an empty cell.
Recall the optimality test
optimal⟺Iij≥0 for every unoccupied cell
If any improvement index is negative, cost can still be reduced.
Select the entering cell
entering cell=(S2,D1)
This cell reduces the total cost fastest per unit re-routed.
Answer
entering cell=(S2,D1)
Question 5
9 markschallenging
The table below shows the cost (in pounds) of transporting one unit from each supply point Si to each demand point Dj, together with the supplies and demands. S1S2S3DemandD12771D24649D387811Supply7104 Use the north-west corner method and the stepping-stone method to find the minimum total transportation cost.
Show worked solution
Worked solution
Apply the north-west corner rule
allocate min(si,dj) starting at the top-left cell
Each step fills the current top-left cell and crosses out an exhausted supply or demand.
Move to a better solution through the entering cell
θ=3 at (S3,D2),I32=−3
The stepping-stone cycle reduces the cost by θ∣Iij∣.
Cost the improved allocation
125+(3)(−3)=116
One iteration is enough here to reach the optimum.
Confirm optimality of the new solution
every improvement index of the new solution≥0
No empty cell can reduce the cost further, so this allocation is optimal.
Recall what a transportation problem asks
mini∑j∑cijxij
The aim is to meet every demand from the available supplies at least total cost.
Recall the balance condition
i∑si=j∑dj
A transportation problem can only be solved once total supply equals total demand.
Recall how a dummy restores balance
dummy supply or demand=i∑si−j∑dj
A dummy row or column with zero costs absorbs the surplus, leaving a balanced problem.
Recall the number of occupied cells needed
occupied cells=m+n−1
A non-degenerate basic feasible solution of an m×n problem fills exactly m+n−1 cells.
Recall the north-west corner rule
start at the top-left cell and allocate as much as possible
Each allocation exhausts a supply or a demand, and we move right or down accordingly.
State the minimum total cost
Cmin=116
This is the least possible total transportation cost.
Answer
116
Unlock 29 more Transportation problems questions
Create a free account to work through every Further Maths Transportation problems question with instant step-by-step worked solutions, progress tracking and interactive lessons.