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Explain solution RD Sharma class 12 Chapter 29 Linear Programming exercise 29.4 question 23

Answers (1)

Answer:

Minimum cost = Rs.92 when 100kg of type I fertilizer and 80 kg of Type II fertilizer is supplied.

Hint:

Form Linear Equation and solve graphically.

Given:

A gardener supply fertilizer of type I which consists of 10% of nitrogen and 6% phosphoric acid and Type II fertilizer which consist of 5% nitrogen and 10% of phosphoric acid. After testing the soil conditions, he finds that he needs at least 14 kg of nitrogen and 14kg of phosphoric acid for two crop of the type I fertilizer cost 60P/Kg and types II fertilizer 40P/Kg

Solution:

Let x kg of Type I fertilizer and y kg of Type II fertilizers are supplied.

The quantity of fertilizers cannot be negative.

So, x, y \geq 0

A gardener has a supply of fertilizer of type I which consists of 10% nitrogen and type II consists of 5% nitrogen, and he needs at least 14kg for his crop.

So,

                (10 \times 100)+(5 \times 100) \geq 14 \\

Or           \begin{aligned} & &10 x+5 y \geq 1400 \end{aligned}

A gardener has a supply of fertilizer of type I which consists of 6% phosphoric acid and type II consists of 10% phosphoric acid, and he needs at least 14 kg of phosphoric acid for his crop.

Sp,

                (6 \times 100)+(10 \times 100) \geq 14 \\

Or           \begin{aligned} & &6 x+10 y \geq 1400 \end{aligned}

Therefore, A/Q, constraint is,

                \begin{aligned} &10 x+5 y \geq 1400 \\ &6 x+10 y \geq 1400 \end{aligned}

If the type I fertilizer costs 60 paise per kg and Type II fertilizer costs 40 paise per kg. Therefore, the cost of x kg of Type 1 fertilizer and y kg of Type II fertilizer is Rs.0.60x and Rs.0.40y respectively.

Total cost=Z(let)=0.6x + 0.4y is to be minimized.

Thus the mathematical formulation of the given LPP ism,

                Min Z=0.6 + 0.4y

Subject to the constraints,

                \begin{aligned} &10 x+5 y \geq 1400 \\ &6 x+10 y \geq 1400 \\ &x, y \geq 0 \end{aligned}

Region represented by 6 x+10 y \geq 1400 : the line 6 x+10 y=1400  passes through  \mathrm{A}\left(\frac{700}{3}, 0\right) , B(0,140). The region which does not contains origin represents solutions of the in equation 6 x+10 y \geq 1400  as (0,0) doesn’t satisfy the in equation 6 x+10 y \geq 1400

Region represented by 10 x+5 y \geq 1400 : the line 10 x+5 y \geq 1400  passes through C(140,0) and D(0,280). The region which does not contains origin represents solutions of the in equation 10 x+5 y \geq 1400  as (0,0) doesn’t satisfy the in equation 10 x+5 y \geq 1400

The region  x, y \geq 0 : represents the first quadrant.

 The corner points are D(0,280),E(100,80), A(700/3,0)

The values of Z at these points are as follows:

                                 

Corner Points

z=0.6x+0.4y

O

0

D

112

E

92

F

140

The minimum value of Z is Rs.92 which is attained at E(100,80)

Thus, the minimum cost is Rs.92 obtained when 100kg of Type I fertilizer and 80 kg of Type II fertilizer is supplied.

 

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