Simplex Furniture
1. **State the problem:** We need to maximize total profit from four furniture types with given constraints using the simplex method.
2. **Define variables:**
Let $x_1, x_2, x_3, x_4$ be the number of Dining Chairs, Tables, Cabinets, and Sofas produced daily.
3. **Objective function (maximize profit):**
$$Z = 80x_1 + 95x_2 + 70x_3 + 120x_4$$
4. **Constraints:**
- Demand limits:
$$x_1 \leq 300$$
$$x_2 \leq 200$$
$$x_3 \leq 400$$
$$x_4 \leq 100$$
- Total machine capacity:
$$400x_1 + 500x_2 + 300x_3 + 600x_4 \leq 250000$$
- Non-negativity:
$$x_1,x_2,x_3,x_4 \geq 0$$
5. **Setup the problem for simplex:**
Express inequalities with slack variables:
$$x_1 + s_1 = 300$$
$$x_2 + s_2 = 200$$
$$x_3 + s_3 = 400$$
$$x_4 + s_4 = 100$$
$$400x_1 + 500x_2 + 300x_3 + 600x_4 + s_5 = 250000$$
Where $s_i \geq 0$ are slack variables representing unused demand or capacity.
6. **Solve using simplex method steps (outline):**
- Start with initial basic feasible solution (all production zero, slack variables take full values).
- Identify entering variable by most positive coefficient in objective function.
- Compute ratios to determine leaving variable.
- Pivot to update the tableau.
- Repeat until no positive coefficients remain in objective row.
7. **Calculate approximate solution by checking capacity and demand:**
Max production by demand limits:
$$x_1=300, x_2=200, x_3=400, x_4=100$$
Machine use:
$$400*300 + 500*200 + 300*400 + 600*100 = 120000 + 100000 + 120000 + 60000 = 400000 > 250000$$
Too high, must reduce.
8. **Strategy:**
Prioritize products with highest profit per machine unit:
$$\text{Profit per machine unit} = \frac{P}{\text{Machine per unit}}$$
Computed as:
- Dining Chair: $\frac{80}{400} = 0.2$
- Table: $\frac{95}{500} = 0.19$
- Cabinet: $\frac{70}{300} \approx 0.233$
- Sofa: $\frac{120}{600} = 0.2$
Highest is Cabinet (0.233), so produce max Cabinets first, then choose others.
9. **Max Cabinets:** $x_3=400$
Capacity used: $300*400=120000$
Remaining capacity: $250000-120000=130000$
10. **Next best profit per machine unit:** Dining Chair or Sofa (0.2), choose Sofa for higher profit/unit.
Max sofas: $x_4=100$
Machine use: $600*100=60000$
Remaining capacity: $130000-60000=70000$
11. **Next Dining Chairs:** each uses 400 units.
Max chairs by remaining capacity: $\lfloor \frac{70000}{400} \rfloor = 175$
Within demand (300), so $x_1=175$
Machine used: $175*400=70000$
Remaining capacity: $0$
12. **Tables:** $x_2=0$ due to capacity limit.
13. **Calculate total profit:**
$$Z = 80*175 + 95*0 + 70*400 + 120*100 = 14000 + 0 + 28000 + 12000 = 54000$$
14. **Final solution:**
Produce 175 Dining Chairs, 0 Tables, 400 Cabinets, and 100 Sofas daily.
This maximizes profit given constraints using the simplex method approach.