Production Optimization
1. **Problem 1:** A company produces two products X and Y with a labor constraint of 240 hours.
Product X requires 4 hours per unit and Y requires 2 hours per unit.
Profit per unit of X is 10, profit per unit of Y is 8.
Maximize profit under the labor constraint.
2. **Step 1:** Define variables.
Let $x$ = units of product X, $y$ = units of product Y.
3. **Step 2:** Set up constraints.
Labor constraint: $$4x + 2y \leq 240$$
4. **Step 3:** Define profit function.
$$P = 10x + 8y$$
5. **Step 4:** Use the labor constraint as equality to maximize profit (since more production means more profit):
$$4x + 2y = 240$$
6. **Step 5:** Express $y$ in terms of $x$:
$$2y = 240 - 4x \Rightarrow y = 120 - 2x$$
7. **Step 6:** Substitute $y$ into profit function:
$$P = 10x + 8(120 - 2x) = 10x + 960 - 16x = 960 - 6x$$
8. **Step 7:** Maximize profit by choosing $x$.
Since profit decreases as $x$ increases (coefficient is -6), profit is maximized at the smallest $x$ that satisfies production non-negativity.
9. **Step 8:** Check if $x=0$ is valid solution:
$$y = 120 - 2(0) = 120$$
Labor use: $$4(0) + 2(120) = 240$$
10. **Step 9:** Profit at $x=0, y=120$:
$$P=10(0) + 8(120)=960$$
Since profit decreases as $x$ increases, producing $0$ units of X and 120 units of Y maximizes profit.
11. **Problem 2:** A firm produces X and Y with labor and capital constraints.
Profit per unit X = 15, for Y = 20.
Labor constraint: $$2x + 3y \leq 240$$
Capital constraint: $$3x + 2y \leq 300$$
12. **Step 1:** Define the objective function:
$$P = 15x + 20y$$
13. **Step 2:** Use Lagrangian method.
Set up Lagrangian:
$$\mathcal{L} = 15x + 20y + \lambda(240 - 2x - 3y) + \mu(300 - 3x - 2y)$$
14. **Step 3:** Compute partial derivatives and set to zero:
$$\frac{\partial \mathcal{L}}{\partial x} = 15 - 2\lambda - 3\mu = 0$$
$$\frac{\partial \mathcal{L}}{\partial y} = 20 - 3\lambda - 2\mu = 0$$
$$\frac{\partial \mathcal{L}}{\partial \lambda} = 240 - 2x - 3y = 0$$
$$\frac{\partial \mathcal{L}}{\partial \mu} = 300 - 3x - 2y = 0$$
15. **Step 4:** Solve the system:
From first two equations:
$$15 = 2\lambda + 3\mu$$
$$20 = 3\lambda + 2\mu$$
16. **Step 5:** Multiply first equation by 3:
$$45 = 6\lambda + 9\mu$$
Multiply second by 2:
$$40 = 6\lambda + 4\mu$$
Subtract second from first:
$$5 = 5\mu \Rightarrow \mu = 1$$
17. **Step 6:** Substitute $\mu$ back to first equation:
$$15 = 2\lambda + 3(1) \Rightarrow 15 = 2\lambda + 3 \Rightarrow 2\lambda = 12 \Rightarrow \lambda = 6$$
18. **Step 7:** Use constraints equations:
$$240 = 2x + 3y$$
$$300 = 3x + 2y$$
19. **Step 8:** Solve for $x,y$.
Multiply first by 3:
$$720 = 6x + 9y$$
Multiply second by 2:
$$600 = 6x + 4y$$
Subtract second from first:
$$120 = 5y \Rightarrow y = 24$$
20. **Step 9:** Substitute $y=24$ into first constraint:
$$240 = 2x + 3(24) = 2x + 72 \Rightarrow 2x=168 \Rightarrow x=84$$
21. **Step 10:** Calculate profit:
$$P=15(84) + 20(24) = 1260 + 480 = 1740$$
**Final answers:**
1. Produce $x=0$, $y=120$ units to maximize profit $960$.
2. Produce $x=84$, $y=24$ units to maximize profit $1740$ using Lagrangian method.