An agricultural firm has 180 tons of nitrogen fertilizer, 250 tons of phosphate and 220 tons of potash. It will be able to sell a mixture of these substances in their respective ratio \(3: 3: 4\) at a profit of Rs. 1500 per ton and a mixture in the ratio \(2: 4: 2\) at a profit of Rs. 1200 per ton. Pose a linear programming problem to show how many tons of these two mixtures should be prepared to obtain the maximum profit.
To formulate a Linear Programming (LP) problem, we need to define the decision variables, the objective function, and the constraints.
Decision Variables
Let:
xx be the number of tons of the mixture in the ratio 3:3:43:3:4 to be prepared.
yy be the number of tons of the mixture in the ratio 2:4:22:4:2 to be prepared.
Objective Function
The firm wants to maximize its profit. The profit for the mixture in the ratio 3:3:43:3:4 is Rs. 1500 per ton, and for the mixture in the ratio 2:4:22:4:2, it is Rs. 1200 per ton. So, the objective function to maximize is:
P=1500 x+1200 yP = 1500x + 1200y
Constraints
The firm has limited amounts of nitrogen fertilizer, phosphate, and potash, so we need to set up constraints based on the availability of these substances.
Certainly! Here is the corrected version with xx and yy replaced by x_(1)x_1 and x_(2)x_2:
Nitrogen Fertilizer Constraint
For the mixture in the ratio 3:3:43:3:4, 3 parts out of 10 are nitrogen fertilizer. So, for every ton of this mixture, (3)/(10)\frac{3}{10} tons of nitrogen fertilizer are used. Similarly, for the mixture in the ratio 2:4:22:4:2, 2 parts out of 8 are nitrogen fertilizer, i.e., (2)/(8)=(1)/(4)\frac{2}{8} = \frac{1}{4} tons of nitrogen fertilizer per ton of mixture. The firm has 180 tons of nitrogen fertilizer available, so:
For the mixture in the ratio 3:3:43:3:4, 3 parts out of 10 are phosphate. So, for every ton of this mixture, (3)/(10)\frac{3}{10} tons of phosphate are used. For the mixture in the ratio 2:4:22:4:2, 4 parts out of 8 are phosphate, i.e., (4)/(8)=(1)/(2)\frac{4}{8} = \frac{1}{2} tons of phosphate per ton of mixture. The firm has 250 tons of phosphate available, so:
For the mixture in the ratio 3:3:43:3:4, 4 parts out of 10 are potash. So, for every ton of this mixture, (4)/(10)\frac{4}{10} tons of potash are used. For the mixture in the ratio 2:4:22:4:2, 2 parts out of 8 are potash, i.e., (2)/(8)=(1)/(4)\frac{2}{8} = \frac{1}{4} tons of potash per ton of mixture. The firm has 220 tons of potash available, so:
Positive maximum C_(j)-Z_(j)C_j-Z_j is 1500 and its column index is 1 . So, the entering variable is x_(1)x_1.
Minimum ratio is 550 and its row index is 3 . So, the leaving basis variable is S_(3)S_3. :.\therefore The pivot element is 8 .
Entering =x_(1)=x_1, Departing =S_(3)=S_3, Key Element =8=8 R_(3)(R_3( new )=R_(3)()=R_3( old )-:8) \div 8 R_(1)(R_1( new )=R_(1)()=R_1( old )-6R_(3)()-6 R_3( new )) R_(2)(R_2( new )=R_(2)()=R_2( old )-3R_(3)()-3 R_3( new ))
Positive maximum C_(j)-Z_(j)C_j-Z_j is 262.5 and its column index is 2 . So, the entering variable is x_(2)x_2.
Minimum ratio is 240 and its row index is 1 . So, the leaving basis variable is S_(1)S_1. :.\therefore The pivot element is 1.25 .
Entering =x_(2)=x_2, Departing =S_(1)=S_1, Key Element =1.25=1.25
{:[R_(1)(” new “)=R_(1)(” old “)-:1.25],[R_(2)(” new “)=R_(2)(” old “)-3.125R_(1)(” new “)],[R_(3)(” new “)=R_(3)(” old “)-0.625R_(1)(” new “)]:}\begin{aligned}
& R_1(\text { new })=R_1(\text { old }) \div 1.25 \\
& R_2(\text { new })=R_2(\text { old })-3.125 R_1(\text { new }) \\
& R_3(\text { new })=R_3(\text { old })-0.625 R_1(\text { new })
\end{aligned}
Since all C_(j)-Z_(j) <= 0C_j-Z_j \leq 0
Hence, optimal solution is arrived with value of variables as :
x_(1)=400,x_(2)=240x_1=400, x_2=240
Max Z=888000\operatorname{Max} Z=888000
Conclusion
Through iterative calculations and optimizations, the LP problem reached an optimal solution where:
x_(1)=400x_1=400 tons (mixture in the ratio 3:3:43: 3: 4 )
x_(2)=240x_2=240 tons (mixture in the ratio 2:4:22: 4: 2 )
Maximum Profit:
The maximum profit that the firm can achieve with this optimal solution is: Max Z=888,000\operatorname{Max} Z=888,000 (in Rs.)