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# The walls and ceiling of a room are to be plastered. The length, breadth and height of the room are 4.5 m, 3 m, and 350 cm respectively. Find the cost of plastering at the rate of Rs 8 per m².

**Solution:**

The __area__ of the four walls and ceiling has to be calculated to find the cost of plastering at the rate of Rs. 8 per m².

Area of the four walls is given as:

Area = 2 × (length × breadth + Breadth × height) - Area of 4 walls + Length × Breadth(Area of ceiling)

Area = 2 × (4.5 × 3.5 + 3 × 3.5) + 4.5 × 3

Area = 2 × (15.75 + 10.5) +13.5

Area = 2 × (26.25) + 13.5

Area = 52.50 + 13.5 = 66.0 m²

The cost of plastering the four walls and ceiling of the room:

Cost = 8 × 66 = Rs. 528

**✦ Try This: **The walls and ceiling of a room are to be plastered. The length, breadth and height of the room are 5 m, 4m, and 450 cm respectively. Find the cost of plastering at the rate of Rs 12 per m².

Area of the four walls is given as:

Area = 2 × (length × breadth + Breadth × height) - Area of 4 walls + Length × Breadth(Area of ceiling)

Area = 2 × (5.0 × 4.5 + 4 × 4.5) + 5 × 4

Area = 2 × (22.5 + 18) + 20

Area = 2 × (40.5) + 20

Area = 81 + 20 = 101 m²

The cost of plastering the four walls and ceiling of the room:

Cost = 12 × 101 = Rs. 1212

**☛ Also Check: **NCERT Solutions for Class 8 Maths Chapter 11

**NCERT Exemplar Class 8 Maths Chapter 11 Problem 65**

## The walls and ceiling of a room are to be plastered. The length, breadth and height of the room are 4.5 m, 3 m, and 350 cm respectively. Find the cost of plastering at the rate of Rs 8 per m².

**Summary:**

The walls and ceiling of a room are to be plastered. The length, breadth and height of the room are 4.5 m, 3 m, and 350 cm respectively. The cost of plastering at the rate of Rs 8 per m².is Rs. 528

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