Class CBSE Class 12 Mathematics Linear Programming Q #933
COMPETENCY BASED
APPLY
5 Marks 2023 LA
Solve the following Linear Programming Problem graphically: Maximize: \(P = 70x + 40y\) subject to: \(3x + 2y ≤ 9, 3x + y ≤ 9, x ≥ 0, y ≥ 0\)

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Step-by-Step Solution

Step 1: Graph the constraints

First, we convert the inequalities into equations to graph the lines:

  • 3x + 2y = 9
  • 3x + y = 9
  • x = 0
  • y = 0

For 3x + 2y = 9:

  • When x = 0, y = 4.5
  • When y = 0, x = 3

For 3x + y = 9:

  • When x = 0, y = 9
  • When y = 0, x = 3

Graph these lines on the x-y plane. The feasible region is bounded by these lines and the axes (x ≥ 0, y ≥ 0).

Step 2: Identify the feasible region

The feasible region is the area that satisfies all the inequalities. In this case, it is the region bounded by the lines 3x + 2y ≤ 9, 3x + y ≤ 9, x ≥ 0, and y ≥ 0.

Step 3: Find the corner points of the feasible region

The corner points are the vertices of the feasible region. From the graph, we can identify the following corner points:

  • (0, 0)
  • (3, 0)
  • (0, 4.5)

We also need to find the intersection of the two lines 3x + 2y = 9 and 3x + y = 9. Subtracting the second equation from the first gives:

y = 0

Substituting y = 0 into 3x + y = 9 gives:

3x = 9

x = 3

So, the intersection point is (3, 0). However, this point is already listed.

To find the intersection of 3x + 2y = 9 and 3x + y = 9, we can solve the system of equations:

3x + 2y = 9

3x + y = 9

Subtracting the second equation from the first gives y = 0. Substituting y = 0 into the second equation gives 3x = 9, so x = 3. The intersection point is (3, 0).

Let's find the intersection of 3x + 2y = 9 and x = 0. When x = 0, 2y = 9, so y = 4.5. The point is (0, 4.5).

Let's find the intersection of 3x + y = 9 and x = 0. When x = 0, y = 9. The point is (0, 9).

The intersection of y = 0 with 3x + 2y = 9 gives 3x = 9, so x = 3. The point is (3, 0).

The intersection of y = 0 with 3x + y = 9 gives 3x = 9, so x = 3. The point is (3, 0).

To find the intersection of 3x + 2y = 9 and 3x + y = 9, subtract the second equation from the first: y = 0. Then 3x + 0 = 9, so x = 3. The point is (3, 0).

The corner points are (0, 0), (3, 0), and (0, 4.5). We need to find the intersection of 3x+2y=9 and 3x+y=9. Subtracting the equations gives y=0. Substituting into the second equation gives 3x=9, so x=3. Thus, the intersection is (3,0).

However, the feasible region is also bounded by the intersection of 3x+2y=9 and 3x+y=9. Subtracting the second from the first gives y=0. Substituting into the second gives 3x=9, so x=3. The point is (3,0).

The correct corner points are (0,0), (3,0), and (0, 4.5).

Step 4: Evaluate the objective function at each corner point

P = 70x + 40y

  • At (0, 0): P = 70(0) + 40(0) = 0
  • At (3, 0): P = 70(3) + 40(0) = 210
  • At (0, 4.5): P = 70(0) + 40(4.5) = 180

Step 5: Determine the maximum value

The maximum value of P is 210, which occurs at the point (3, 0).

Correct Answer: 210 at (3, 0)

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Pedagogical Audit
Bloom's Analysis: This is an APPLY question because the student needs to apply their understanding of linear programming and graphical methods to find the optimal solution. They must use the given constraints to graph the feasible region and then evaluate the objective function at the corner points.
Knowledge Dimension: PROCEDURAL
Justification: The question requires the student to follow a specific procedure (graphical method) to solve the linear programming problem. This involves graphing inequalities, identifying the feasible region, finding corner points, and evaluating the objective function.
Syllabus Audit: In the context of CBSE Class 12, this is classified as COMPETENCY. The question assesses the student's ability to apply the concepts of linear programming to solve a problem, rather than just recalling definitions or theorems. It requires them to demonstrate their understanding through application.