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ML Aggarwal Solutions Class 8 Mathematics Solutions for Mensuration Exercise 18.4 in Chapter 18 - Mensuration

Question 10 Mensuration Exercise 18.4

A rectangular room is 6 m long, 5 m wide and 3.5 m high. It has 2 doors of size 1·1 m by 2 m and 3 windows of size 1.5 m by 1.4 m. Find the cost of whitewashing the walls and the ceiling of the room at the rate of ₹5.30 per square meter.

Answer:

Given, Length of room = 6 m

Breadth of room = 5 m

Height of room = 3.5 m

So, Area of four walls = 2 (l + b) × h

= 2 (6 + 5) × 3.5

= 77 m2

Area of 2 doors and 3 windows = (2 × 1.1 × 2 + 3 × 1.5 × 1.4)

= (44 + 6.3) m2

= 10.7 m2

Area of ceiling = l × b = 6 × 5 = 30 m2

Thus,

Total area for white washing = (77 – 10.7 + 30) m2 = 96.3 m2

Hence, the cost of whitewashing = ₹(96.3 × 5.30) = ₹510.39

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