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Consider the linear programming problem(LPP):

Minimize Z=x+yZ = x + y

x+2y≤4,x + 2y \leq 4,

3x+y≥3,3x + y \geq 3,

4x+3y≥6,4x + 3y \geq 6,

x,y≥0.x, y \geq 0.

Which of the following is correct for the above linear programming problem (LPP):

(A) The LPP has a bounded feasible region.

(B) The LPP has a unique optimal solution.

(C) The optimal value of the LPP exists at the point (3/2, 0)

(D) The corner points of the feasible region are (3/2, 0), (3/5, 6/5), (2/5, 6/5) and (4, 0)

Choose the correct answer from the options given below:

Solution

✅ Correct Option: 2

We need to minimize Z=x+yZ = x + y subject to:

x+2y≤4,3x+y≥3,4x+3y≥6,x,y≥0x + 2y \leq 4, \quad 3x + y \geq 3, \quad 4x + 3y \geq 6, \quad x, y \geq 0


Intersection of 4x+3y=64x + 3y = 6 and y=0y = 0:

4x=64x = 6

x=32x = \tfrac{3}{2}

Corner point: (32,  0)\left(\tfrac{3}{2},\; 0\right)


Intersection of 4x+3y=64x + 3y = 6 and 3x+y=33x + y = 3:

From 3x+y=33x + y = 3:   y=3−3x\;y = 3 - 3x

4x+3(3−3x)=64x + 3(3 - 3x) = 6

4x+9−9x=64x + 9 - 9x = 6

−5x=−3-5x = -3

x=35x = \tfrac{3}{5}

y=3−95=65y = 3 - \tfrac{9}{5} = \tfrac{6}{5}

Corner point: (35,  65)\left(\tfrac{3}{5},\; \tfrac{6}{5}\right)


Intersection of 3x+y=33x + y = 3 and x+2y=4x + 2y = 4:

From 3x+y=33x + y = 3:   y=3−3x\;y = 3 - 3x

x+2(3−3x)=4x + 2(3 - 3x) = 4

x+6−6x=4x + 6 - 6x = 4

−5x=−2-5x = -2

x=25x = \tfrac{2}{5}

y=3−65=95y = 3 - \tfrac{6}{5} = \tfrac{9}{5}

Corner point: (25,  95)\left(\tfrac{2}{5},\; \tfrac{9}{5}\right)

Note: this point is (25,  95)\left(\tfrac{2}{5},\;\tfrac{9}{5}\right), not (25,  65)\left(\tfrac{2}{5},\;\tfrac{6}{5}\right).


Intersection of x+2y=4x + 2y = 4 and y=0y = 0:

x=4x = 4

Corner point: (4,  0)\left(4,\; 0\right)


The corner points are: (32,0)\left(\tfrac{3}{2}, 0\right), (35,65)\left(\tfrac{3}{5}, \tfrac{6}{5}\right), (25,95)\left(\tfrac{2}{5}, \tfrac{9}{5}\right), and (4,0)(4, 0).

Since all four corners close off the region, the feasible region is bounded.


Evaluating Z=x+yZ = x + y at each corner:

At (32,  0)\left(\tfrac{3}{2},\; 0\right): Z=32=1.5Z = \tfrac{3}{2} = 1.5

At (35,  65)\left(\tfrac{3}{5},\; \tfrac{6}{5}\right): Z=95=1.8Z = \tfrac{9}{5} = 1.8

At (25,  95)\left(\tfrac{2}{5},\; \tfrac{9}{5}\right): Z=115=2.2Z = \tfrac{11}{5} = 2.2

At (4,  0)(4,\; 0): Z=4Z = 4

Zmin⁡=32Z_{\min} = \dfrac{3}{2} at (32,  0)\left(\dfrac{3}{2},\; 0\right)

Since no other corner gives the same minimum and Z=x+y=32Z = x + y = \tfrac{3}{2} is not parallel to any edge touching this corner, the solution is unique.


(A) Bounded feasible region — Correct, the region is enclosed on all sides.

(B) Unique optimal solution — Correct, only one point gives Z=32Z = \tfrac{3}{2}.

(C) Optimal at (32,0)\left(\tfrac{3}{2}, 0\right) — Correct.

(D) Corner points include (25,65)\left(\tfrac{2}{5}, \tfrac{6}{5}\right) — Wrong, the correct point is (25,95)\left(\tfrac{2}{5}, \tfrac{9}{5}\right).


The answer is (A), (B) and (C) only.

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