Math Problem Statement

Objective : max 2.9x + 1.8y Subject to the constraints: 4y + 5x ≤ 20 8y + 15x ≤ 48 Find the maximum value!

(Notes: Use 4 digits after decimal point)

Solution

To solve this linear programming problem, we will use the method of finding the feasible region defined by the constraints and then evaluating the objective function at each vertex of this region.

Objective Function:

Maximize Z=2.9x+1.8y\text{Maximize } Z = 2.9x + 1.8y

Constraints:

  1. 4y+5x204y + 5x \leq 20
  2. 8y+15x488y + 15x \leq 48
  3. x0x \geq 0
  4. y0y \geq 0

Step 1: Convert the inequalities to equalities to find the intersection points (vertices).

  1. Constraint 1: 4y+5x=204y + 5x = 20
    y=205x4=51.25xy = \frac{20 - 5x}{4} = 5 - 1.25x

  2. Constraint 2: 8y+15x=488y + 15x = 48
    y=4815x8=61.875xy = \frac{48 - 15x}{8} = 6 - 1.875x

Step 2: Find the intersection points of the constraints with the axes.

  • For 4y+5x=204y + 5x = 20:

    • When x=0x = 0: y=5y = 5
    • When y=0y = 0: x=4x = 4

    Points: (0,5)(0, 5) and (4,0)(4, 0)

  • For 8y+15x=488y + 15x = 48:

    • When x=0x = 0: y=6y = 6
    • When y=0y = 0: x=3.2x = 3.2

    Points: (0,6)(0, 6) and (3.2,0)(3.2, 0)

Step 3: Find the intersection point of the two constraints.

4y+5x=204y + 5x = 20 8y+15x=488y + 15x = 48

Multiply the first equation by 2: 8y+10x=408y + 10x = 40

Subtract the first from the second: 8y+15x(8y+10x)=48408y + 15x - (8y + 10x) = 48 - 40 5x=85x = 8 x=85=1.6x = \frac{8}{5} = 1.6

Substitute x=1.6x = 1.6 into 4y+5x=204y + 5x = 20: 4y+5(1.6)=204y + 5(1.6) = 20 4y+8=204y + 8 = 20 4y=124y = 12 y=3y = 3

Intersection point: (1.6,3)(1.6, 3)

Step 4: Evaluate the objective function at each vertex.

  1. At (0,5)(0, 5):
    Z=2.9(0)+1.8(5)=0+9=9Z = 2.9(0) + 1.8(5) = 0 + 9 = 9

  2. At (4,0)(4, 0):
    Z=2.9(4)+1.8(0)=11.6+0=11.6Z = 2.9(4) + 1.8(0) = 11.6 + 0 = 11.6

  3. At (3.2,0)(3.2, 0):
    Z=2.9(3.2)+1.8(0)=9.28+0=9.28Z = 2.9(3.2) + 1.8(0) = 9.28 + 0 = 9.28

  4. At (1.6,3)(1.6, 3):
    Z=2.9(1.6)+1.8(3)=4.64+5.4=10.04Z = 2.9(1.6) + 1.8(3) = 4.64 + 5.4 = 10.04

Step 5: Conclusion

The maximum value of ZZ is 11.6000 at the point (4,0)(4, 0).

Would you like any additional details or have any questions?

Here are 5 related questions for further exploration:

  1. How would the solution change if the objective function was to minimize 2.9x+1.8y2.9x + 1.8y?
  2. What happens to the feasible region if we change the constraint 4y+5x204y + 5x \leq 20 to 4y+5x154y + 5x \leq 15?
  3. How can we solve this problem graphically to verify the solution?
  4. What are the implications if there are no feasible solutions for a set of constraints?
  5. How would we approach this problem if there were more than two variables?

Tip: Always check for the feasibility of the intersection points with the original constraints, as not all calculated points may be within the feasible region.

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Math Problem Analysis

Mathematical Concepts

Linear Programming
Optimization
Inequalities

Formulas

Objective Function: Z = 2.9x + 1.8y
Constraints: 4y + 5x ≤ 20, 8y + 15x ≤ 48
Intersection of lines: Solve linear equations to find vertices

Theorems

Fundamental Theorem of Linear Programming (vertex evaluation)

Suitable Grade Level

Grades 10-12