Linear Programming
1. The problem is to minimize the objective function $$z = 40x + 50y$$ subject to the constraints:
$$2x + y \geq 24$$
$$x + y \geq 16$$
$$x + 2y \geq 20$$
$$x, y \geq 0$$
2. We find the feasible region defined by these inequalities and then check the values of $$z$$ at each vertex (corner point) of this region.
3. Find the vertices by solving the system for the intersections of the constraints:
- Intersection of $$2x + y = 24$$ and $$x + y = 16$$:
Subtract equations:
$$ (2x + y) - (x + y) = 24 - 16 \implies x = 8 $$
Substitute $$x=8$$ into $$x + y =16$$:
$$8 + y = 16 \implies y = 8$$
So, vertex at $$(8,8)$$.
- Intersection of $$2x + y = 24$$ and $$x + 2y = 20$$:
From $$2x + y = 24$$, rewrite $$y = 24 - 2x$$
Substitute into $$x + 2y = 20$$:
$$x + 2(24 - 2x) = 20 \implies x + 48 - 4x = 20 \implies -3x = -28 \implies x = \frac{28}{3}$$
Then $$y = 24 - 2 \times \frac{28}{3} = 24 - \frac{56}{3} = \frac{72}{3} - \frac{56}{3} = \frac{16}{3}$$
So, vertex at $$\left(\frac{28}{3}, \frac{16}{3}\right)$$.
- Intersection of $$x + y = 16$$ and $$x + 2y = 20$$:
From $$x + y =16$$, rewrite $$x = 16 - y$$
Substitute into $$x + 2y = 20$$:
$$16 - y + 2y = 20 \implies 16 + y = 20 \implies y = 4$$
Then $$x = 16 - 4 = 12$$
So, vertex at $$(12, 4)$$.
4. Verify these vertices satisfy $$x, y \geq 0$$ and all constraints (which they do).
5. Compute $$z = 40x + 50y$$ at each vertex:
- At $$(8,8)$$:
$$z = 40 \times 8 + 50 \times 8 = 320 + 400 = 720$$
- At $$\left(\frac{28}{3}, \frac{16}{3}\right)$$:
$$z = 40 \times \frac{28}{3} + 50 \times \frac{16}{3} = \frac{1120}{3} + \frac{800}{3} = \frac{1920}{3} = 640$$
- At $$(12,4)$$:
$$z = 40 \times 12 + 50 \times 4 = 480 + 200 = 680$$
6. The minimum value of $$z$$ among these is $$640$$ at $$\left(\frac{28}{3}, \frac{16}{3}\right)$$.
**Final answer:**
Minimum value of $$z$$ is $$640$$ at $$\left(\frac{28}{3}, \frac{16}{3}\right)$$.