Two godowns A and B have grain capacities of 100 quintals and 50 quintals respectively. They supply to 3 ration shops, D, E and F, whose requirements are 60, 50 and 40 quintals respectively. The cost of transportation per quintal from the godowns to the shops are given in the following table:
Transportation cost per quintal (in Rs) From/ To A B D64E32F2.503
How would the supplies be transported in order that the transportation cost is miniumum? What is the minimum cost?
Ley godown A supplies x and y quintals of grain to the shops D and E respectively.
Then, (100 - x - y) will be supplied to shop F.
The requirement at shop D is 60 quintals, Since x quintals are transported from godown A. Therefore, the remaining (60 - x)quintals are transported from godown B. Similarly, (50 - y) quintals and 40 - (100 - x - y) = (x + y - 60) quintals will be transported from godown B to shops E and F respectively. The given problem can be represented diagrammatically as follows:
Ley Z be the total cost of transportation then,
Z = 6x + 3y + 2.50(100 - x - y)+4(60 - x)+2(50 - y) +3(x + y) - 60
=6x + 3y + 250 - 2.5x - 2.5y + 240 - 4x + 100 - 2y + 3x + 3y - 180
=2.50x + 1.50y + 410
Subject to constraints are 60−x≥0⇔x≤60 (ii)50−y≥0⇔y≤50 (iii)100−(x+y)≥0⇔x+y≤100 (iv)x+y−60≥⇔x+y≥60 (v)x≥0, y≥0 (vi)Firstly, draw the graph of the line x+y=100, we have0+0≤100⇒0≤100 (which is true)So, the half plane is towards the origin.Secondly, draw the graph of the line x=60Putting (0, 0) in the inequality x+y≤100,we have 0≤60 (Which is true)So, the half plane is towards the origin.Thirdly, draw the graph of the line x+y=60x060y600
Putting (0, 0) in the inequality x + y≥ 60, we have 0+0≥60 ⇒ 0≥60(which is false)So, the half plane is away from the origin. Fourthly, draw the graph of the line y = 50 putting(0, 0) in the inequality y≤50, we have 0≤50(which is true)So, the half plane is towards the origin. Since, x, y ≥0 So, the feasible region lies in the first quadrant. The intersection points of the given lines are A (60, 0), B(60, 40), C(50, 50) and D(10, 50).
∴~~Feasible region is ABCDA.
The corner points of the feasible region are A(60, 0) B(60, 40), C(50, 50) and D(10, 50). The values of Z at these points are as follows:
Corner pointZ=2.5x+1.5y+410A(60, 0)560B(60, 40)620C(50, 50)610D(10, 50) 510→minimum
The minimum value of Z is 510 at D(10, 50).
Thus, the amount of grain transported from A to D, E and F is 10 quintals, 50 quintals and 40 quintals respectively and from B to D, E and F is 50 quintals, 0 quintal and 0 quintal respectively.
The minimum cost is Rs. 510.