Find solution using Simplex method (BigM method)
MAX Z = 30x1 + 40x2
subject to
3x1 + 2x2 <= 600
3x1 + 5x2 <= 800
5x1 + 6x2 <= 1100
and x1,x2 >= 0; Solution:Problem is | Max `Z` | `=` | `` | `30` | `x_1` | ` + ` | `40` | `x_2` |
|
| subject to |
| `` | `3` | `x_1` | ` + ` | `2` | `x_2` | ≤ | `600` | | `` | `3` | `x_1` | ` + ` | `5` | `x_2` | ≤ | `800` | | `` | `5` | `x_1` | ` + ` | `6` | `x_2` | ≤ | `1100` |
|
| and `x_1,x_2 >= 0; ` |
The problem is converted to canonical form by adding slack, surplus and artificial variables as appropiate
1. As the constraint-1 is of type '`<=`' we should add slack variable `S_1`
2. As the constraint-2 is of type '`<=`' we should add slack variable `S_2`
3. As the constraint-3 is of type '`<=`' we should add slack variable `S_3`
After introducing slack variables| Max `Z` | `=` | `` | `30` | `x_1` | ` + ` | `40` | `x_2` | ` + ` | `0` | `S_1` | ` + ` | `0` | `S_2` | ` + ` | `0` | `S_3` |
|
| subject to |
| `` | `3` | `x_1` | ` + ` | `2` | `x_2` | ` + ` | `` | `S_1` | | | | | | | = | `600` | | `` | `3` | `x_1` | ` + ` | `5` | `x_2` | | | | ` + ` | `` | `S_2` | | | | = | `800` | | `` | `5` | `x_1` | ` + ` | `6` | `x_2` | | | | | | | ` + ` | `` | `S_3` | = | `1100` |
|
| and `x_1,x_2,S_1,S_2,S_3 >= 0` |
| `Z` | ` - ` | `30` | `x_1` | ` - ` | `40` | `x_2` | | | | | | | | | | = | `0` |
|
| `` | `3` | `x_1` | ` + ` | `2` | `x_2` | ` + ` | `` | `S_1` | | | | | | | = | `600` | | `` | `3` | `x_1` | ` + ` | `5` | `x_2` | | | | ` + ` | `` | `S_2` | | | | = | `800` | | `` | `5` | `x_1` | ` + ` | `6` | `x_2` | | | | | | | ` + ` | `` | `S_3` | = | `1100` |
|
Simplex tableau is
Tableau-0
| `"Basis"` | `x_1` | `x_2` | `S_1` | `S_2` | `S_3` | `RHS` | |
| `R_1` `Z` | `-30` | `-40` | `0` | `0` | `0` | `0` | |
| `R_2` `S_1` | `3` | `2` | `1` | `0` | `0` | `600` | |
| `R_3` `S_2` | `3` | `5` | `0` | `1` | `0` | `800` | |
| `R_4` `S_3` | `5` | `6` | `0` | `0` | `1` | `1100` | |
Tableau-1
| `"Basis"` | `x_1` | `x_2``darr` | `S_1` | `S_2` | `S_3` | `RHS` | `"Ratio"=(RHS)/(x_2)` |
| `R_1` `Z` | `-30` | `-40` | `0` | `0` | `0` | `0` | |
| `R_2` `S_1` | `3` | `2` | `1` | `0` | `0` | `600` | `(600)/(2)=300` |
| `R_3` `S_2` | `3` | `(5)` | `0` | `1` | `0` | `800` | `(800)/(5)=160``->` |
| `R_4` `S_3` | `5` | `6` | `0` | `0` | `1` | `1100` | `(1100)/(6)=183.3333` |
Most Negative `Z` is `-40`. So,
the entering variable is `x_2`.
Minimum ratio is `160`. So,
the leaving basis variable is `S_2`.
`:.`
The pivot element is `5`.
Entering `=x_2`, Departing `=S_2`, Key Element `=5`
`R_3`(new)`= R_3`(old) `-: 5`
| `x_1` | `x_2` | `S_1` | `S_2` | `S_3` | `RHS` |
| `R_3`(old) = | `3` | `5` | `0` | `1` | `0` | `800` |
| `R_3`(new)`= R_3`(old) `-: 5` | `0.6` | `1` | `0` | `0.2` | `0` | `160` |
`R_2`(new)`= R_2`(old) - `2 R_3`(new)
| `x_1` | `x_2` | `S_1` | `S_2` | `S_3` | `RHS` |
| `R_2`(old) = | `3` | `2` | `1` | `0` | `0` | `600` |
| `R_3`(new) = | `0.6` | `1` | `0` | `0.2` | `0` | `160` |
| `2 xx R_3`(new) = | `1.2` | `2` | `0` | `0.4` | `0` | `320` |
| `R_2`(new)`= R_2`(old) - `2 R_3`(new) | `1.8` | `0` | `1` | `-0.4` | `0` | `280` |
`R_4`(new)`= R_4`(old) - `6 R_3`(new)
| `x_1` | `x_2` | `S_1` | `S_2` | `S_3` | `RHS` |
| `R_4`(old) = | `5` | `6` | `0` | `0` | `1` | `1100` |
| `R_3`(new) = | `0.6` | `1` | `0` | `0.2` | `0` | `160` |
| `6 xx R_3`(new) = | `3.6` | `6` | `0` | `1.2` | `0` | `960` |
| `R_4`(new)`= R_4`(old) - `6 R_3`(new) | `1.4` | `0` | `0` | `-1.2` | `1` | `140` |
`R_1`(new)`= R_1`(old) - `-40 R_3`(new)
| `x_1` | `x_2` | `S_1` | `S_2` | `S_3` | `RHS` |
| `R_1`(old) = | `-30` | `-40` | `0` | `0` | `0` | `0` |
| `R_3`(new) = | `0.6` | `1` | `0` | `0.2` | `0` | `160` |
| `-40 xx R_3`(new) = | `-24` | `-40` | `0` | `-8` | `0` | `-6400` |
| `R_1`(new)`= R_1`(old) - `-40 R_3`(new) | `-6` | `0` | `0` | `8` | `0` | `6400` |
Tableau-2
| `"Basis"` | `x_1``darr` | `x_2` | `S_1` | `S_2` | `S_3` | `RHS` | `"Ratio"=(RHS)/(x_1)` |
| `R_1` `Z` | `-6` | `0` | `0` | `8` | `0` | `6400` | |
| `R_2` `S_1` | `1.8` | `0` | `1` | `-0.4` | `0` | `280` | `(280)/(1.8)=155.5556` |
| `R_3` `x_2` | `0.6` | `1` | `0` | `0.2` | `0` | `160` | `(160)/(0.6)=266.6667` |
| `R_4` `S_3` | `(1.4)` | `0` | `0` | `-1.2` | `1` | `140` | `(140)/(1.4)=100``->` |
Most Negative `Z` is `-6`. So,
the entering variable is `x_1`.
Minimum ratio is `100`. So,
the leaving basis variable is `S_3`.
`:.`
The pivot element is `1.4`.
Entering `=x_1`, Departing `=S_3`, Key Element `=1.4`
`R_4`(new)`= R_4`(old) `-: 1.4`
| `x_1` | `x_2` | `S_1` | `S_2` | `S_3` | `RHS` |
| `R_4`(old) = | `1.4` | `0` | `0` | `-1.2` | `1` | `140` |
| `R_4`(new)`= R_4`(old) `-: 1.4` | `1` | `0` | `0` | `-0.8571` | `0.7143` | `100` |
`R_2`(new)`= R_2`(old) - `1.8 R_4`(new)
| `x_1` | `x_2` | `S_1` | `S_2` | `S_3` | `RHS` |
| `R_2`(old) = | `1.8` | `0` | `1` | `-0.4` | `0` | `280` |
| `R_4`(new) = | `1` | `0` | `0` | `-0.8571` | `0.7143` | `100` |
| `1.8 xx R_4`(new) = | `1.8` | `0` | `0` | `-1.5429` | `1.2857` | `180` |
| `R_2`(new)`= R_2`(old) - `1.8 R_4`(new) | `0` | `0` | `1` | `1.1429` | `-1.2857` | `100` |
`R_3`(new)`= R_3`(old) - `0.6 R_4`(new)
| `x_1` | `x_2` | `S_1` | `S_2` | `S_3` | `RHS` |
| `R_3`(old) = | `0.6` | `1` | `0` | `0.2` | `0` | `160` |
| `R_4`(new) = | `1` | `0` | `0` | `-0.8571` | `0.7143` | `100` |
| `0.6 xx R_4`(new) = | `0.6` | `0` | `0` | `-0.5143` | `0.4286` | `60` |
| `R_3`(new)`= R_3`(old) - `0.6 R_4`(new) | `0` | `1` | `0` | `0.7143` | `-0.4286` | `100` |
`R_1`(new)`= R_1`(old) - `-6 R_4`(new)
| `x_1` | `x_2` | `S_1` | `S_2` | `S_3` | `RHS` |
| `R_1`(old) = | `-6` | `0` | `0` | `8` | `0` | `6400` |
| `R_4`(new) = | `1` | `0` | `0` | `-0.8571` | `0.7143` | `100` |
| `-6 xx R_4`(new) = | `-6` | `0` | `0` | `5.1429` | `-4.2857` | `-600` |
| `R_1`(new)`= R_1`(old) - `-6 R_4`(new) | `0` | `0` | `0` | `2.8571` | `4.2857` | `7000` |
Tableau-3
| `"Basis"` | `x_1` | `x_2` | `S_1` | `S_2` | `S_3` | `RHS` | |
| `R_1` `Z` | `0` | `0` | `0` | `2.8571` | `4.2857` | `7000` | |
| `R_2` `S_1` | `0` | `0` | `1` | `1.1429` | `-1.2857` | `100` | |
| `R_3` `x_2` | `0` | `1` | `0` | `0.7143` | `-0.4286` | `100` | |
| `R_4` `x_1` | `1` | `0` | `0` | `-0.8571` | `0.7143` | `100` | |
Since all `Z_j >= 0`
Hence, optimal solution is arrived with value of variables as :
`x_1=100,x_2=100`
Max `Z=7000`
This material is intended as a summary. Use your textbook for detail explanation.
Any bug, improvement, feedback then