Question

exercise 13.1 of first question of
ncert math of 9class

Answer 1

Answer:

For question refer to the attachment.

Given that, Length = 1.5 m

Breadth = 1.25 m

Height = 0.65 m

It is to be made open at the top. Hence area of sheet required would be:

Total Surface area of the Box - Area of the top Face

Total Surface area of the box = 2 ( lb + bh + hl )

=> TSA = 2 ( 1.5 * 1.25 + 1.25 * 0.65 + 0.65 * 1.5 )

=> TSA = 2 ( 1.875 + 0.975 + 0.8125 )

=> TSA = 2 ( 3.6625 )

=> TSA = 7.325 m²

Area of top face = L × B => 1.5 * 1.25 = 1.875

=> Area of sheet required = 7.325 - 1.875 = 5.45 m²

Cost per m² = Rs. 20

=> Cost for 5.45 m² is 5.45 * 20 = 109

Hence the area of sheet required is 5.45 m² and cost is Rs. 109.

Answer 2

HEY MATE HERE IS YOUR ANSWER

$\bold {QUESTION :-}$ A Plastic Box 1.5m long, 1.25m wide and 65m deep is to be made. It is opened at the top. Ignoring the thickness of the plastic sheet, determine.

(i) The area of sheet required for making the box.
(ii) The cost of sheet for it, a sheet measuring 1m^2 costs Rs 20.

$\huge \bold {Solutions :-}$

(i)
length of plastic box ☐ = 1.5m
Breadth of plastic box ☐ = 1.25m
Height of plastic box ☐ = 65cm
Height in metres = 65 / 100 = 0.65m

C. S. A of plastic box + top = 2h( l +b) + l× b

➡️ 2 × 0.65( 1.5 + 1.25)+ 1.5 × 1.25
➡️Rs. 5.45 m^2

(ii)

Cost of 1m^2 sheet Rs 20.

Cost of Rs 5.45^2 = 5.45 × 20 = Rs. 109


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Hope it will help you