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Provide Solution for RD Sharma Class 12 Chapter 29 Linear Programming Exercise 29.4 Question 39

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Answer: The number of book of I type is 12 and II type is 6

Hint:

Let, two types of books be x and y.

Given:

Thickness of the books=6cm and 4 cm

Weight of the books=1 kg and 1 \frac{1}{2} kg each

Shelf is 9 cm and at most can support a weight of 21 kg

Solution:

Let two types of books be x and y respectively.

The required LPP is maximized.

Z=x+y

Subject to the constraints,

6 x+4 y \leq 96\; Or \; 3 x+2 y \leq 48

x+\frac{3}{2} y \leq 21 \text { Or } 2 x+3 y \leq 42

And   x, y \geq 0

On considering the inequalities as equations,

We get,

                                 3 x+2 y=48                                     …(i)

                                 \begin{aligned} &\\ &2 x+3 y=42 \end{aligned}                                     … (ii)

Table for line  3 x+2 y=48  is

 

x

0

16

y

24

0

 

So, it passes through (0, 24) and (16,0)

On putting (0, 0) in 3 x+2 y \leq 48 ,

 We get   0 \leq 48   [Which is true]

Table for  2 x+3 y=42

x

0

21

y

14

0

 

So it passes through (0, 14) and (21, 0)

On putting (0, 0) in 2 x+3 y \leq 42 ,

We get  0 \leq 42  [Which is true]

On solving equation (i) and (ii), we get

                              X = 12 and y = 6

Thus, the intersection point is B (12, 6)

From the graph, OABCD is the feasible region which is bounded. The corner points are O(0,0) A(0,14), B(12,6) and C(16,0)

The values of Z at corner points are as follows.

Corner Points

Z=x+y

O(0,0)

Z=0+0=0

A(0,14)

Z=0+14=14

B(12,6)

Z=12+6=18

C(16,0)

Z=16+0=16

 

From the table, the maximum value of Z is 18 at B(12,6)

Hence, the maximum number of books is 18 and number of books of I type is 12 and books of II type is 6.

 

 

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