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CBSE - Class 12 Mathematics Linear Programming Worksheet
EXERCISE 12.1
Worksheet Answers
Solution:
The objective function to be optimized is $Z = x + 2y$. The constraints are defined as follows:
To identify the feasible region, we solve for the boundary lines by converting inequalities to equalities:
| Line | Equation | Intercepts/Points |
|---|---|---|
| $L_1$ | $x + 2y = 100$ | $(0, 50), (100, 0)$ |
| $L_2$ | $y = 2x$ | $(0, 0), (40, 80)$ |
| $L_3$ | $2x + y = 200$ | $(0, 200), (100, 0)$ |
Intersection Calculations:
The feasible region is the polygon defined by vertices $(20, 40), (50, 100),$ and $(100, 0)$. We evaluate $Z = x + 2y$ at these points [Per the Corner Point Theorem]:
| Corner Point $(x, y)$ | $Z = x + 2y$ |
|---|---|
| $(20, 40)$ | $20 + 2(40) = 100$ |
| $(50, 100)$ | $50 + 2(100) = 250$ |
| $(100, 0)$ | $100 + 2(0) = 100$ |
The value of $Z$ is 100 at both $(20, 40)$ and $(100, 0)$. Since the objective function is linear, $Z$ will be 100 at all points on the line segment connecting $(20, 40)$ and $(100, 0)$.
Final Solution: The minimum value of $Z$ is 100 at all points on the line segment joining $(20, 40)$ and $(100, 0)$; the maximum value of $Z$ is 250 at the point $(50, 100)$.
Solution:
The objective function to be maximized is $Z = -x + 2y$. The constraints are defined as follows:
To identify the feasible region, we convert inequalities into equations to find the boundary lines:
| Constraint | Equation | Intercept Points |
|---|---|---|
| $L_1$ | $x = 3$ | Vertical line at $x = 3$ |
| $L_2$ | $x + y = 5$ | $(5, 0)$ and $(0, 5)$ |
| $L_3$ | $x + 2y = 6$ | $(6, 0)$ and $(0, 3)$ |
Determining Intersection Points:
The feasible region is unbounded, extending toward infinity in the positive direction of $x$ and $y$. However, we test the vertices of the boundary:
| Corner Point $(x, y)$ | $Z = -x + 2y$ |
|---|---|
| $(3, 2)$ | $-3 + 2(2) = 1$ |
| $(4, 1)$ | $-4 + 2(1) = -2$ |
| $(6, 0)$ | $-6 + 2(0) = -6$ |
Per the [Corner Point Theorem for unbounded regions], we check if any point in the feasible region yields a value of $Z$ greater than the maximum found at the vertices. For $Z = -x + 2y$, as $x \to \infty$ and $y \to \infty$ along the constraint $x+y=5$, $Z$ can increase indefinitely. However, check the constraint $Z > 1$: $-x + 2y > 1$. This region overlaps with the feasible region. Therefore, the function $Z = -x + 2y$ has no finite maximum value.
Final Solution: The Linear Programming Problem has no finite maximum value because the feasible region is unbounded and the objective function $Z$ can increase indefinitely.
Solution:
We aim to optimize the objective function $Z = 5x + 10y$ subject to the following system of linear inequalities:
To identify the feasible region, we define the boundary lines:
| Line | Equation | Intercepts/Points |
|---|---|---|
| $L_1$ | $x + 2y = 120$ | $(120, 0), (0, 60)$ |
| $L_2$ | $x + y = 60$ | $(60, 0), (0, 60)$ |
| $L_3$ | $x - 2y = 0$ | $(0, 0), (40, 20), (60, 30)$ |
The feasible region is the intersection of the half-planes defined by the constraints. [Per the Graphical Method for LPP], we test the origin $(0,0)$ or convenient points:
The vertices of the feasible region are found by solving the intersection of the boundary lines:
| Corner Point | $Z = 5x + 10y$ |
|---|---|
| $(40, 20)$ | $5(40) + 10(20) = 200 + 200 = 400$ |
| $(60, 30)$ | $5(60) + 10(30) = 300 + 300 = 600$ |
| $(0, 60)$ | $5(0) + 10(60) = 0 + 600 = 600$ |
Final Solution: The minimum value of $Z$ is $400$ at point $(40, 20)$, and the maximum value of $Z$ is $600$ at all points on the segment joining $(60, 30)$ and $(0, 60)$.
Solution:
We are given the objective function $Z = -3x + 4y$ which is to be minimized, subject to the following system of linear inequalities:
To determine the feasible region, we solve for the boundary lines by converting inequalities to equalities:
Solving the system of linear equations to find the vertex where the two constraint lines meet:
$x + 2y = 8$ ... (Eq. i)
$3x + 2y = 12$ ... (Eq. ii)
Subtracting (Eq. i) from (Eq. ii): $(3x - x) + (2y - 2y) = 12 - 8 \implies 2x = 4 \implies x = 2$.
Substituting $x = 2$ into (Eq. i): $2 + 2y = 8 \implies 2y = 6 \implies y = 3$.
The point of intersection is $(2, 3)$.
The feasible region is bounded by the vertices $(0, 0)$, $(4, 0)$, $(2, 3)$, and $(0, 4)$. We evaluate $Z = -3x + 4y$ at each point:
| Corner Point $(x, y)$ | $Z = -3x + 4y$ |
|---|---|
| $(0, 0)$ | $-3(0) + 4(0) = 0$ |
| $(4, 0)$ | $-3(4) + 4(0) = -12$ |
| $(2, 3)$ | $-3(2) + 4(3) = -6 + 12 = 6$ |
| $(0, 4)$ | $-3(0) + 4(4) = 16$ |
Comparing the values obtained: $0, -12, 6, 16$. The minimum value is $-12$, which occurs at the point $(4, 0)$. [Per the Corner Point Theorem for Linear Programming].
Final Solution: The minimum value of $Z$ is $-12$ at the point $(4, 0)$.
Solution:
The objective function to be minimized is $Z = x + 2y$. The constraints are defined as follows:
To plot the feasible region, we convert the inequalities into equations:
Solving the system of equations $2x + y = 3$ and $x + 2y = 6$ simultaneously:
Multiply the first equation by 2: $4x + 2y = 6$. Subtracting the second equation ($x + 2y = 6$):
$(4x - x) = 6 - 6 \implies 3x = 0 \implies x = 0$. Substituting $x=0$ into $2x + y = 3$ yields $y = 3$.
The region is bounded by the axes and these lines. Testing $(1, 2)$ shows that the shaded area lies to the right/above the lines.
Since the region is unbounded in the first quadrant, we check the corner points identified by the boundary lines:
| Corner Point $(x, y)$ | $Z = x + 2y$ |
|---|---|
| $(0, 3)$ | $0 + 2(3) = 6$ |
| $(6, 0)$ | $6 + 2(0) = 6$ |
At both $(0, 3)$ and $(6, 0)$, $Z = 6$. We check if any point on the line segment connecting $(0, 3)$ and $(6, 0)$ provides a value less than 6. The line segment lies on $x + 2y = 6$. For any point $(x, y)$ on this segment, $x + 2y = 6$. Thus, $Z = 6$ for all points on the segment $x + 2y = 6$ between $x=0$ and $x=6$.
Since the problem asks for the minimum, and any point on the segment gives $Z=6$ (which is consistent with the constraint $x + 2y \geq 6$), the minimum occurs at infinitely many points along this boundary.
Final Solution: The minimum value of $Z$ is $6$, which occurs at all points on the line segment joining $(0, 3)$ and $(6, 0)$.
Solution:
We are tasked with maximizing the objective function $Z = 5x + 3y$ subject to the following non-negative and linear constraints:
To identify the feasible region, we convert the inequalities into equations to find the line intercepts:
| Equation | $x$-intercept $(y=0)$ | $y$-intercept $(x=0)$ |
|---|---|---|
| $3x + 5y = 15$ | $(5, 0)$ | $(0, 3)$ |
| $5x + 2y = 10$ | $(2, 0)$ | $(0, 5)$ |
Solve the system of linear equations to find the intersection of the two boundary lines [By Algebraic Elimination Method]:
Multiply the first equation by 2 and the second by 5:
$6x + 10y = 30$
$25x + 10y = 50$
Subtract the first from the second: $19x = 20 \implies x = \frac{20}{19} \approx 1.05$
Substitute $x$ into $5x + 2y = 10$: $5(\frac{20}{19}) + 2y = 10 \implies \frac{100}{19} + 2y = \frac{190}{19} \implies 2y = \frac{90}{19} \implies y = \frac{45}{19} \approx 2.37$
The feasible region is bounded by the vertices $(0,0)$, $(2,0)$, $(\frac{20}{19}, \frac{45}{19})$, and $(0,3)$ [Per the Corner Point Theorem].
| Corner Point $(x, y)$ | $Z = 5x + 3y$ |
|---|---|
| $(0, 0)$ | $5(0) + 3(0) = 0$ |
| $(2, 0)$ | $5(2) + 3(0) = 10$ |
| $(0, 3)$ | $5(0) + 3(3) = 9$ |
| $(\frac{20}{19}, \frac{45}{19})$ | $5(\frac{20}{19}) + 3(\frac{45}{19}) = \frac{100 + 135}{19} = \frac{235}{19} \approx 12.37$ |
Final Solution: The maximum value of $Z$ is $\frac{235}{19}$ occurring at the point $(\frac{20}{19}, \frac{45}{19})$.
Solution:
To determine the boundary lines of the feasible region, we treat the given constraints as equations:
We calculate the coordinates for the boundary lines:
| Line | $x$-intercept ($y=0$) | $y$-intercept ($x=0$) |
|---|---|---|
| $x + 3y = 3$ | $(3, 0)$ | $(0, 1)$ |
| $x + y = 2$ | $(2, 0)$ | $(0, 2)$ |
To find the vertex of the feasible region, solve the system of equations:
$x + 3y = 3$
$x + y = 2$
Subtracting the second equation from the first: $(x + 3y) - (x + y) = 3 - 2 \implies 2y = 1 \implies y = 0.5$.
Substituting $y = 0.5$ into $x + y = 2$: $x + 0.5 = 2 \implies x = 1.5$.
The intersection point is $(1.5, 0.5)$.
The feasible region is unbounded and defined by the vertices formed by the constraints $x+3y \geq 3$ and $x+y \geq 2$ in the first quadrant. The corner points are:
| Corner Point | $Z = 3x + 5y$ |
|---|---|
| $(0, 2)$ | $3(0) + 5(2) = 10$ |
| $(1.5, 0.5)$ | $3(1.5) + 5(0.5) = 4.5 + 2.5 = 7$ |
| $(3, 0)$ | $3(3) + 5(0) = 9$ |
For an unbounded region, we check if $3x + 5y < 7$ has any common points with the feasible region. Setting $3x + 5y < 7$, we find no intersection, as the minimum value $7$ at $(1.5, 0.5)$ satisfies the constraints and provides the absolute minimum.
Final Solution: The minimum value of $Z$ is $7$ at the point $(1.5, 0.5)$.
Solution:
We are given the objective function $Z = 3x + 2y$ to be maximized, subject to the following system of linear inequalities (constraints):
To plot the lines, we determine the intercepts for each equation:
| Line | $x$-intercept $(y=0)$ | $y$-intercept $(x=0)$ |
|---|---|---|
| $x + 2y = 10$ | $(10, 0)$ | $(0, 5)$ |
| $3x + y = 15$ | $(5, 0)$ | $(0, 15)$ |
To find the intersection of the two lines, we solve the system of linear equations:
Substituting $(2)$ into $(1)$:
$x + 2(15 - 3x) = 10$The feasible region is bounded by the vertices $(0, 0)$, $(5, 0)$, $(4, 3)$, and $(0, 5)$. We test these points in $Z = 3x + 2y$:
| Corner Point $(x, y)$ | $Z = 3x + 2y$ |
|---|---|
| $(0, 0)$ | $3(0) + 2(0) = 0$ |
| $(5, 0)$ | $3(5) + 2(0) = 15$ |
| $(4, 3)$ | $3(4) + 2(3) = 12 + 6 = 18$ |
| $(0, 5)$ | $3(0) + 2(5) = 10$ |
Comparing the values, the maximum value of $Z$ is $18$.
Final Solution: The maximum value of $Z$ is 18 at the point $(4, 3)$.
Solution:
We are given the objective function $Z = x + y$, which is to be maximized subject to the following system of linear inequalities (constraints):
To determine the region, we analyze the boundary lines individually:
Observe the constraints simultaneously:
These two inequalities imply $x + 1 \leq y \leq x$, which simplifies to $x + 1 \leq x$, or $1 \leq 0$. [By the law of trichotomy and basic algebraic inconsistency].
Since the inequality $x - y \leq -1$ requires $y \geq x + 1$ and the inequality $-x + y \leq 0$ requires $y \leq x$, there exists no set of points $(x, y)$ that satisfies both conditions simultaneously. The region defined by the intersection of these half-planes is an empty set (null set). Consequently, there is no feasible region.
Final Solution: The Linear Programming Problem has no feasible solution, and therefore, no maximum value for $Z$ exists.
Solution:
Given the objective function: $Z = 3x + 4y$ (to be maximized).
The constraints are defined as:
We convert the inequality constraints into equations to determine the boundary lines of the feasible region:
The feasible region is the triangle formed by the vertices $(0, 0)$, $(4, 0)$, and $(0, 4)$ [By the definition of the solution set for $x, y \geq 0$ and the half-plane $x + y \leq 4$].
| Corner Point | $Z = 3x + 4y$ |
|---|---|
| $(0, 0)$ | $3(0) + 4(0) = 0$ |
| $(4, 0)$ | $3(4) + 4(0) = 12$ |
| $(0, 4)$ | $3(0) + 4(4) = 16$ |
The Fundamental Theorem of Linear Programming states that the maximum value of the objective function occurs at a corner point of the feasible region. Comparing the values obtained at the vertices: $0, 12, 16$. The maximum value is $16$.
Final Solution: The maximum value of $Z$ is $16$ at the point $(0, 4)$.