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Solve the following L.P.P. by graphical method : Minimize : Z = 7x + y subject to 5x + y ≥ 5, x + y ≥ 3, x ≥ 0, y ≥ 0. - Mathematics and Statistics

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Question

Solve the following L.P.P. by graphical method :

Minimize : Z = 7x + y subject to 5x + y ≥ 5, x + y ≥ 3, x ≥ 0, y ≥ 0.

Graph
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Solution

To draw the feasible region, construct table as follows:

Inequality 5x + y ≥ 5 x + y ≥ 3
Corresponding equation (of line) 5x + y = 5 x + y = 3
Intersection of line with X-axis (1, 0) (3, 0)
Intersection of line with Y-axis (0, 5) (0, 3)
Region Non-origin side Non-origin side


Shaded portion XABCY is the feasible region,
whose vertices are A(3, 0), B and C (0, 5).
B is the point of intersection of the lines x + y = 3 and 5x + y = 5
Solving the above equations, we get

x = `(1)/(2), y = (5)/(2)`

∴ B ≡ `(1/2, 5/2)`
Here, the objective function is Z = 7x + y
Z at A(3, 0) = 7(3) + 0 = 21

Z at B`(1/2, 5/2) = 7(1/2) + (5)/(2)`

= `(7)/(2) + (5)/(2)` = 6
Z at C (0, 5) = 7(0) + 5 = 5
∴ Z has minimum value 5 at C(0, 5).
∴ Z is minimum, when x = 0 and y = 5.

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Chapter 6: Linear Programming - Exercise 6.2 [Page 101]

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