A rectangula sheet of tin 45 cm by 24 cmis to be made into

Question 2:- A rectangula sheet of tin 45 cm by 24 cmis to be made into a box without top, by cutting of square from each corner and folding up the flaps. What should be the side of square to be cutt of so that the volume of the box is maximum?

Solution: Length and breadth of rectangular sheets 45 cm and 24 cm respectively.

Let side of each of the four squares cut off from each corner = x cm

Let Z denote the volume of the box

Vlume of box (Z)=l.b.h

Z = (45-2x)(24-2x)x

\Rightarrow Z = (1080-138x +4x^2)x

\Rightarrow Z = 1080x -138x^2+4x^3

Now differentiating with respect to x

\frac{dZ}{dx} = 1080 - 276x +12x^2

and \frac{d^2Z}{dx^2} = -276 +24x

\text { For Max and minima } \frac{d z}{d x}=0

12 x^2-276 x+1080=0

=x^2-23 x+90=0

(x-5)(x-18)=0

x=5 \text { or } x=18

x=18 is rejected because at x=18 length =24-2 x=18-2 \times 18=-12 which is impossible.

Here x=5 is the turning point.

\text { At } x=5,

\frac{d^2 z}{d x^2}=24 \times 3-276=-156 \text { [Negative] }

z is maximum at x=5 that is, side of each square to be cut off from each corner for maximum volume is 5 \mathrm{~cm}.

Question 1:- A square piece of tin of side 18 cm is to be made into a box without top, by cutting a square from each corner and folding up the flaps to form the box. What should be the side of the square to be cut off so that the volume of the box is the maximum possible?

Solution:- For solution click here

Question 3:- Show that of all the rectangles inscribed in a given fixed circle, the square has maximum area.

Solution: For solution click here

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