Question

ND VOLUMES
EXERCISE 13.1
box 1.5 m long, 1.25 m wide and 65 cm deep
oring the thickness of the plastic sheet, dete
area of the sheet required for making the bo
cost of sheet for it, if a sheet 1m2​

Answer 1

Answer:

The dimension of the box is

Length l= 1.5 m

Breadth b= 1.25 m

Height h= 65 cm = 0.65 m

Area of the sheet required is

A=2lb+2bh+2lhA=2lb+2bh+2lh

A=2(1.5)(1.25)+2(1.25)(0.65)+2(1.5)(0.65)A=2(1.5)(1.25)+2(1.25)(0.65)+2(1.5)(0.65)

A=1.95+1.625+1.875A=1.95+1.625+1.875

A=5.45m^2A=5.45m

2

The area of the sheet required for making the box is 5.45 meter square.

ii) The cost of sheet for it, if a sheet measuring 7m×3.5m costsर 510.

i.e, area of sheet 24.5 meter square cost Rs.510

So, 1 meter square cost \frac{510}{24.5}=20.816

24.5

510

=20.816

Now, The cost of 5.45 meter square cost

20.816\times 5.45=113.44720.816×5.45=113.447

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Therefore, The cost of sheet is Rs. 113.447.

Answer 2

Question :-

A plastic box 1.5 m long, 1.25 m wide and 65 cm deep is to be made. It is opened at the top. Ignoring the thickness of the plastic sheet, determine

(i) The area of the sheet required for making the box.

(ii) The cost of sheet for it, if a sheet measuring 1m2 costs ₹20.

Answer :-

(i) Here, length (l) = 1.5 m, bread th(b) = 1 .25 m

and height (h) = 65 cm = 65/100 m = 0.65 m

∵ It is open from the top.

∴ Its surface area

= [Lateral surface area] + [Base area]

= [2(1 + b)h] + [lb]

= [2(1.50 + 1.25)0.65] m2 + [1.50 x 1.25] m2

= [2 x 2.75 x 0.65] m2 + [1.875] m2

= 3.575 m2+ 1.875 m2 = 5.45 m2

∴ Area of the sheet required for making the box = 5.45 m2

(ii) Cost of 1 m2 sheet = Rs. 20

Cost of 5.45 m2 sheet = Rs. (20 x 5.45)

= Rs. 109

Hence, cost of the required sheet = Rs. 109

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