Question

the Length breadth and height of a room are 5 metre for metre and 3 metre respectively find the cost of whitewashing the walls of the room and the ceiling @ rupees 7.50 per metre square ​

Answer 1

Answer:

Length of the room = 5 m

Breadth of the room = 4 m

Height of the room = 3 m

Walls that need to white washed = Lateral Surface Area + Area of Ceiling

Lateral Surface area of a Cuboid = 2h ( l + b )

Substituting the values we get,

⇒ 2 × 3 ( 5 + 4 )

⇒ 2 × 3 × 9

⇒ 54 m²

Area of Ceiling = Length × Breadth

⇒ Area of Ceiling = 5 × 4 = 20 m²

Total Area to be Whitewashed = 54 m² + 20 m² = 74 m²

Cost per m² = Rs. 7.50

⇒ Cost = 74 m² × Rs. 7.50

⇒ Cost = Rs. 555

Therefore cost for whitewashing is Rs. 555.

Answer 2

$\boxed{\green{\sf Answer}}$

Rs. 555

$\boxed{\green{\sf Explanation}}$

Given:

• Length = 5m
• height = 3m
• breadth = 4m
• cost for white washing=Rs.7.50/m²

To Find:

Cost for white washing the walls of the room and ceiling

Solution:

L.S.A. of the Room

$\boxed{\green{L.S.A. \: of \: cuboid = 2h(l+b)}}$

$\mathsf{L.S.A = 2(3)[5+4]}$

$\mathsf{L.S.A = 6[9]}$

$\mathsf{L.S.A = 54{m}^{2}}$

Area of ceiling

$\boxed{\green{Area \: of \: rectangle = lb}}$

$\mathsf{Area\: of \: ceiling = 5 \times 4}$

$\mathsf{Area \: of \: ceiling = 20{m}^{2}}$

Total Area:

Total area = L.S.A. of room + area of ceiling

TOTAL AREA = 54 + 20= 74m²

Cost for white washing 74m²

Cost for white washing 1m² = rs. 7.50

Cost for white washing 74m² is

$\mathsf{\implies 74 \times 7.50}$

$\mathsf{\implies Rs.555}$