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A Room 5 M Long, 4.5 M Wide, and 3.6 M High Have One Door 1.5 M by 2.4 M and Two Windows, Each 1 M by 0.75 M. Find : (I) the Area of Its Walls, Excluding Door and Windows - Mathematics

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Sum

A room 5 m long, 4.5 m wide, and 3.6 m high have one door 1.5 m by 2.4 m and two windows, each 1 m by 0.75 m. Find :
(i) the area of its walls, excluding door and windows ;
(ii) the cost of distempering its walls at the rate of Rs.4.50 per m2.
(iii) the cost of painting its roof at the rate of Rs.9 per m2.

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Solution

Length of the room = 5 m
The breadth of the room = 4.5 m
Height of the room = 3.6 m

Area of the roof = `"L" xx "B"`

= `5 xx 4.5`m2

= 22.5 m2

Area of four walls = 2[L + B] × H

= 2[5 + 4.5] × 3.6

= 2(9.5) × 3.6

= 19 × 3.6

= 68.4 m2

Area of one door = `1.5 xx 2.4 "m"^2`

= 3.60 m2

= 3.6 m2

Area of one window = `1 xx 0.75`m2

= 0.75 m2

Area of 2 window = `0.75 xx 2`m2

= 1.5 m2

(i) Area of four walls excluding door and windows = 68.4 - (3.6 + 1.5)

= 68.4 - 5.1

= 63.3 m2

(ii) Cost of distempering four walls @ Rs. 4.50 per m2

= 63.3 × 4.50

= Rs. 284.85

(iii) Cost of painting the roof  @ Rs.9 per m2

= 22.5 × 9

= Rs. 202.50 

Concept: Surface Area of a Cuboid
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APPEARS IN

Selina Concise Mathematics Class 8 ICSE
Chapter 21 Surface Area, Volume and Capacity
Exercise 21 (B) | Q 4 | Page 240
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