4. Unbalanced supply and demand example
Unbalanced supply and demand
If the total supply is not equal to the total demand then the problem is called unbalanced transportation problem.
It's solution :
1. If the total supply is more than the total demand, then we add a new column, with transportation cost 0
2. If the total demand is more than the total supply, then we add a new row, with transportation cost 0
Example
Find Solution using North-West Corner method
| D1 | D2 | D3 | Supply | S1 | 4 | 8 | 8 | 76 | S2 | 16 | 24 | 16 | 82 | S3 | 8 | 16 | 24 | 77 | Demand | 72 | 102 | 41 | |
Solution: TOTAL number of supply constraints : 3 TOTAL number of demand constraints : 3 Problem Table is
| `D_1` | `D_2` | `D_3` | | Supply | `S_1` | 4 | 8 | 8 | | 76 | `S_2` | 16 | 24 | 16 | | 82 | `S_3` | 8 | 16 | 24 | | 77 | | Demand | 72 | 102 | 41 | | |
Here Total Demand = 215 is less than Total Supply = 235. So We add a dummy demand constraint with 0 unit cost and with allocation 20. Now, The modified table is
| `D_1` | `D_2` | `D_3` | `D_(dummy)` | | Supply | `S_1` | 4 | 8 | 8 | 0 | | 76 | `S_2` | 16 | 24 | 16 | 0 | | 82 | `S_3` | 8 | 16 | 24 | 0 | | 77 | | Demand | 72 | 102 | 41 | 20 | | |
The rim values for `S_1`=76 and `D_1`=72 are compared.
The smaller of the two i.e. min(76,72) = 72 is assigned to `S_1` `D_1`
This meets the complete demand of `D_1` and leaves 76 - 72=4 units with `S_1`
Table-1
| `D_1` | `D_2` | `D_3` | `D_(dummy)` | | Supply | `S_1` | 4(72) | 8 | 8 | 0 | | 4 | `S_2` | 16 | 24 | 16 | 0 | | 82 | `S_3` | 8 | 16 | 24 | 0 | | 77 | | Demand | 0 | 102 | 41 | 20 | | |
Move horizontally,
The rim values for `S_1`=4 and `D_2`=102 are compared.
The smaller of the two i.e. min(4,102) = 4 is assigned to `S_1` `D_2`
This exhausts the capacity of `S_1` and leaves 102 - 4=98 units with `D_2`
Table-2
| `D_1` | `D_2` | `D_3` | `D_(dummy)` | | Supply | `S_1` | 4(72) | 8(4) | 8 | 0 | | 0 | `S_2` | 16 | 24 | 16 | 0 | | 82 | `S_3` | 8 | 16 | 24 | 0 | | 77 | | Demand | 0 | 98 | 41 | 20 | | |
Move vertically,
The rim values for `S_2`=82 and `D_2`=98 are compared.
The smaller of the two i.e. min(82,98) = 82 is assigned to `S_2` `D_2`
This exhausts the capacity of `S_2` and leaves 98 - 82=16 units with `D_2`
Table-3
| `D_1` | `D_2` | `D_3` | `D_(dummy)` | | Supply | `S_1` | 4(72) | 8(4) | 8 | 0 | | 0 | `S_2` | 16 | 24(82) | 16 | 0 | | 0 | `S_3` | 8 | 16 | 24 | 0 | | 77 | | Demand | 0 | 16 | 41 | 20 | | |
Move vertically,
The rim values for `S_3`=77 and `D_2`=16 are compared.
The smaller of the two i.e. min(77,16) = 16 is assigned to `S_3` `D_2`
This meets the complete demand of `D_2` and leaves 77 - 16=61 units with `S_3`
Table-4
| `D_1` | `D_2` | `D_3` | `D_(dummy)` | | Supply | `S_1` | 4(72) | 8(4) | 8 | 0 | | 0 | `S_2` | 16 | 24(82) | 16 | 0 | | 0 | `S_3` | 8 | 16(16) | 24 | 0 | | 61 | | Demand | 0 | 0 | 41 | 20 | | |
Move horizontally,
The rim values for `S_3`=61 and `D_3`=41 are compared.
The smaller of the two i.e. min(61,41) = 41 is assigned to `S_3` `D_3`
This meets the complete demand of `D_3` and leaves 61 - 41=20 units with `S_3`
Table-5
| `D_1` | `D_2` | `D_3` | `D_(dummy)` | | Supply | `S_1` | 4(72) | 8(4) | 8 | 0 | | 0 | `S_2` | 16 | 24(82) | 16 | 0 | | 0 | `S_3` | 8 | 16(16) | 24(41) | 0 | | 20 | | Demand | 0 | 0 | 0 | 20 | | |
Move horizontally,
The rim values for `S_3`=20 and `D_(dummy)`=20 are compared.
The smaller of the two i.e. min(20,20) = 20 is assigned to `S_3` `D_(dummy)`
Table-6
| `D_1` | `D_2` | `D_3` | `D_(dummy)` | | Supply | `S_1` | 4(72) | 8(4) | 8 | 0 | | 0 | `S_2` | 16 | 24(82) | 16 | 0 | | 0 | `S_3` | 8 | 16(16) | 24(41) | 0(20) | | 0 | | Demand | 0 | 0 | 0 | 0 | | |
Initial feasible solution is
| `D_1` | `D_2` | `D_3` | `D_(dummy)` | | Supply | `S_1` | 4 (72) | 8 (4) | 8 | 0 | | 76 | `S_2` | 16 | 24 (82) | 16 | 0 | | 82 | `S_3` | 8 | 16 (16) | 24 (41) | 0 (20) | | 77 | | Demand | 72 | 102 | 41 | 20 | | |
The minimum total transportation cost `=4 xx 72+8 xx 4+24 xx 82+16 xx 16+24 xx 41+0 xx 20=3528`
Here, the number of allocated cells = 6 is equal to m + n - 1 = 3 + 4 - 1 = 6 `:.` This solution is non-degenerate
This material is intended as a summary. Use your textbook for detail explanation. Any bug, improvement, feedback then
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