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Need solution for RD Sharma Maths Class 12 Chapter 29 Linear Programmig Excercise 29.4 Question 17

Answers (1)

Answer:

Min\: cost = Rs 254 when 14 units of compound A and 33 unit compound B are produced.

Hint:

Form Linear Equation and solve graphically.

Given:

A chemical company produces two compounds A and B . The following table gives the units of ingredients C and D per kg of Compounds A and B as well as minimum requirement of C and D and costs per kg of A and B

 

compound

Minimum

 

A

B

requirement

Ingredient C

1

2

80

Ingredient D

3

1

75

Cost(inE) perkg

4

6

 

Solution:

Let required quantity of compound A and B are x and y kg. Since, cost of 1 kg of compound A and B are Rs.4 and Rs.6 per kg. So, Cost of x kg compound A and y kg of compound B are Rs.4x and Rs.6 respectively.

Let z be the total cost of compounds.

So,z= 4x + 6y

Since compound A and B contain 1 and 2 units of ingredient C per kg respectively , So x kg of Compound A and y kg of Compound B contain x and 2y units of ingredient C respectively but minimum requirement of ingredient C is 80 units.

So ,
x+2y\geq 80                                    {first constraint}

Since, compound A and B contain 3 and 1 units of ingredient D per kg respectively.

So x kg of compound A and y kg of compound B contain 3x and y units of ingredient D respectively but minimum requirement of ingredient C is 75 units

So ,

3x+y\geq 75                                 {Second constraint}
Hence mathematical formulation of the given L.P.P is,

Min  z = 4x + 6 y
Subject to constraints,

\begin{aligned} &x+2 y \geq 80 \\ &5 x+y \geq 75 \\ & \end{aligned}

x, y \geq 0 [Since production cannot be less than 0]

Region represented by x+2y\geq 80  : The line x+2y=80  meets the axes at A(80,0) , B(0,40) respectively.

Region not containing represents x+2y=80  as (0,0) does not satisfy satisfies  x+2y=80

Region  3x-1y\geq 75   : line  3x+y=75  meets axes at C(25,0),D(0,7)  respectively.
Region not containing origin represents  3x-1y\geq 75  as (0,0) does not satisfy 3x-1y\geq 75 .
Region  x,y\geq 0:   it represents first quadrant.

The corner points are D(0,75),\epsilon (14,33),A(80,0)  .

The value of z at these corner points are as follows.

Corner Points

z=4x+6y

D

450

ε

254

A

320

The minimum value of z is 254 which is attained at \epsilon (14,33)
Thus, the minimum cost is Rs. 254 obtained when 14 units of compound A and 33 units compound B are produced.

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