Question

A manufacturer makes two products A and B. Product A sells at Rs 200 each and takes 1/2 hour to make. Product B sells at Rs 300 each and takes 1 hour to make. There is a permanent order for 14 of product A and 16 of product B. A working week consists of 40 hours of production and weekly turnover must not be less than Rs 10000. If the profit on each of product A is Rs 20 and on product B is Rs 30, then how many of each should be produced so that the profit is maximum. Also, find the maximum profit.

Answer 1

Let x units of product A and y units of product B were manufactured.
Number of units cannot be negative.
Therefore, $x,y\ge 0$

According to question, the given information can be tabulated as:

	Selling price(Rs)	Manufacturing time(hrs)
Product A(x)	200	0.5
Product B(y)	300	1

Also, the availability of time is 40 hours and the revenue should be atleast Rs 10000.

Further, it is given that there is a permanent order for 14 units of product A and 16 units of product B.

Therefore, the constraints are
$$\begin{gathered} 200x+300y\ge 10000 \\ 0.5x+y\le 40 \\ x\ge 14 \\ y\ge 16 \end{gathered}$$

If the profit on each of product A is Rs 20 and on product B is Rs 30.Therefore, profit gained on x units of product A and y units of product B is Rs 20x and Rs 30y respectively.

Total profit = Z = $20x+30y$ which is to be maximised

Thus, the mathematical formulat​ion of the given linear programmimg problem is

Max Z = $20x+30y$

subject to

$$\begin{gathered} 2x+3y\ge 100 \\ x+2y\le 80 \\ x\ge 14 \\ y\ge 16 \end{gathered}$$
$x,y\ge 0$

First we will convert inequations into equations as follows:
2x + 3y = 100, x + 2y = 80, x = 14, y = 16, x = 0 and y = 0.

Region represented by 2x + 3y ≥ 100:
The line 2x + 3y = 100 meets the coordinate axes at A₁(50, 0) and $B_1\left(0,\frac{100}{3}\right)$ respectively. By joining these points we obtain the line
2x + 3y = 100 . Clearly (0,0) does not satisfies the 2x + 3y = 100. So, the region which does not contain the origin represents the solution set of the inequation 2x + 3y ≥ 100.

Region represented by x + 2y ≤ 80:
The line x + 2y = 80 meets the coordinate axes at C₁(80, 0) and D₁(0, 40) respectively. By joining these points we obtain the line
x + 2y = 80. Clearly (0,0) satisfies the inequation x + 2y ≤ 80. So,the region which contains the origin represents the solution set of the inequation x + 2y ≤ 80.

Region represented by x ≥ 14
x = 14 is the line passes through (14, 0) and is parallel to the Y axis.The region to the right of the line x = 14 will satisfy the inequation.

Region represented by y ≥ 16
y = 16 is the line passes through (0, 16) and is parallel to the X axis.The region above the line y = 16 will satisfy the inequation.

Region represented by x ≥ 0 and y ≥ 0:
Since, every point in the first quadrant satisfies these inequations. So, the first quadrant is the region represented by the inequations x ≥ 0, and y ≥ 0.

The feasible region determined by the system of constraints 2x + 3y ≥ 100, x + 2y ≤ 80, x ≥ 14, y ≥ 16, x ≥ 0 and y ≥ 0 are as follows.


The corner points of the feasible region are E₁(26, 16), F₁(48, 16), G₁(14, 33) and H₁(14, 24)

The values of Z at these corner points are as follows

Corner point	Z= 20x + 30y
E1	1000
F1	1440
G1	1270
H1	1000

The maximum value of Z is Rs 1440 which is attained at F₁$\left(48,16\right)$.

Thus, the maximum profit is Rs 1440 obtained when 48 units of product A and 16 units of product B were manufactured.