Given:
Maximize \(Z=3 x+5 y\)
Subject to:
\(x+2 y \leq 20 \)
\(x+y \leq 15 \)
\(y \leq 5 \)
\(x, y \geq 0\)
We need to maximize \(\mathrm{Z}=3 x+5 y\)
First, we will convert the given inequations into equations, we obtain the following equations:
\(x+2 y=20, x+y=15, y=5, x=0\) and \(y=0\)
The line \(x+2 y=20\) meets the coordinate axis at \(A(20,0)\) and \(B(0,10)\). Join these points to obtain the line \(x+2 y=20\), \((0,0)\) satisfies the inequation \(x+2 y \leq 20\).
So, the region in \(x y\)-plane that contains the origin represents the solution set of the given equation.
The line \(x+y=15\) meets the coordinate axis at \(C(15,0)\) and \(D(0,15)\). Join these points to obtain the line \(x+y=15\). \((0,0)\) satisfies the inequation \(x+y \leq 15 .\) So, the region in \(x y\)-plane that contains the origin represents the solution set of the given equation.
\(y=5\) is the line passing through \((0,5)\) and parallel to the \(X\) axis.The region below the line \(y=5\) will satisfy the given inequation.
Region represented by \(x \geq 0\) and \(y \geq 0\) :
Since, every point in the first quadrant satisfies these inequations. So, the first quadrant is the region represented by the inequations.
These lines are drawn using a suitable scale.
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The corner points of the feasible region are \(O(0,0), C(15,0), E(10,5)\) and \(F(0,5)\) The values of \(Z\) at these corner points are as follows.
\(\begin{array}{|l|l|} \hline \text{Corner point} & Z=3 x+5 y \\ \hline O(0,0) & 3 \times 0+5 \times 0=0 \\ \hline C(15,0) & 3 \times 15+5 \times 0=45 \\ \hline E(10,5) & 3 \times 10+5 \times 5=55 \\ \hline F(0,5) & 3 \times 0+5 \times 5=25 \\ \hline \end{array}\)
We see that the maximum value of the objective function \(Z\) is 55 which is at \(E(10,5)\).
Thus, the optimal value of \(Z\) is 55.