Question

The length,breadth and height of a room is 5 m, 4 m and 3 m. The cost of whitewashing its four walls at the rate of Rs.7.50 per sq.m is

Answer 1

Given :

The length, breadth and height of a room is 5 m, 4 m and 3 m.

To find :

The cost of whitewashing its four walls at the rate of Rs.7.50 per m² .

Solution :

· Length = 5 m

· Breadth = 4 m

· Height = 3 m

⭑ Area of 4 walls = LSA of the cuboidal room.

⭑ LSA of cuboid = 2(l + b) × h

So atq,

⇒ Area of 4 walls = 2(5 + 4) × 3

⇒ Area of 4 walls = 2 × 9 × 3

⇒ Area of 4 walls = 54 m²

⭑ Rate of whitewashing = Rs. 7.50/m²

⇒ Cost of whitewashing = Area of 4 walls × Rate

⇒ Cost of whitewashing = 54 × 7.50

⇒ Cost of whitewashing = Rs. 405

∴ Cost of whitewashing its 4 walls = Rs. 405

Answer 2

Given

• Length of cuboid = 5 m
• Breadth of cuboid = 4 m
• Height of cuboid - 3 m
• Cost of white washing its 4 walls = Rs 7.50 / m²

To find

• Cost of white washing its 4 walls

Solution

We are asked to find the cost of white washing cuboid 4 walls, that means the lateral surface area of cuboid, L.S.A means 4 walls.

• L.S.A of cuboid = 2h (l + b)

Substituting the values, we get :-

• L.S.A = 2(3) (5 + 4)
• L.S.A = 6 (9)
• L.S.A= 54

Hence, the area of 4 walls is 54 m²

Now, we have :-

• 1 m² - Rs 7.50
• 54 m² - ?
• 54 m² - 54 × 7.50
• 54 m² - 405

Hence, the cost of white washing the four walls of the room or the cuboid is 405 m²

Learn more

• Total surface area of cuboid = 2(lb + bh + hl)
• Volume of cuboid = l × b × h
• Diagonal of cuboid = √l² + b² + h²

Where :-

• l - length
• b - breadth
• h - height