Question

The length, breadth and height of a room are 5 m, 4 m and 3 m respectively. Find the cost white washing the walls of the room and ceiling at the rate of Rs. 7.50 per m 2
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Answer 1

Answer:

Length, breadth and height of a room are 5 m, 4 m and 3 m.

Area of four walls of the room =2h(l+b)

=2×3(5+4)

=6(9)

=54 sq m

Area of the ceiling =l×b

=5×4

=20 sq cm.

Total area of the four walls and the ceiling of the room

=54+20

=74 sq cm

Cost of white washing = Rs 7.50 per sq m

Total cost of white washing =74×7.50= Rs 555

Step-by-step explanation:

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Answer 2

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Given:-

Dimensions of room = 5m × 4m × 3m

Cost of whitewashing = ₹7.50 per m²

To find:-

Cost of whitewashing the walls + ceiling.

Solution:-

$\boxed{Curved \: surface \: area \: of cuboid= 2h(l +b)}$

Where,

l = Length

b = Breadth

h = height

On substituting the values -

$\boxed{Curved \: surface \: area \: of \: cuboid = 2h(l+b)}$

CSA of room = 2 × 3(5 + 4)m³

CSA of room = 6(9)m³

CSA of room = 54m³

Since, ceiling is in the shape of rectangle we will use the formula of area of rectangle.

$\boxed{Area \: of \: ceiling = L × B}$

Area of ceiling = 5 × 4m

Area of Ceiling = 20m²

Area of the whitewashing the room + ceiling = Area of four walls + Area of ceiling

Area of whitewashing the room

= 54 + 20m = 74m³

Cost of whitewashing the wall and ceiling of room = Area of room × cost given

Cost of whitewashing the wall and ceiling

= 74 × 7.50 = ₹555

∴ The cost of whitewashing the walls and ceiling is ₹555