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Mensuration 1 | Mensuration 1 Exercise 20.1

Question 20

A room is 9 m long, 8 m broad and 6.5 m high. It has one door of dimensions 2 m x 1.5 m and three windows each of dimensions 1.5 m x 1 m. Find the cost of white washing the walls at Rs 3.80 per square meter.

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Given Length of a room = 9 m

Breadth of a room = 8 m

Height of a room = 6.5 m

Area of 4 walls = 2(1 + b) h

= 2 (9 m + 8 m) x 6.5 m

= 2 x 17 m x 6.5 m

= 221 m^2

Length of a door = 2 m

Breadth of a door = 1.5 m

Area of a door = Length x Breadth

= 2 m x 1.5 m

= 3 m^2

Length of a window = 1.5 m

Breadth of a window = 1 m

Since, area of one window = Length x Breadth

= 1.5 m x 1 m

= 1.5 m^2

Thus, Area of 3 such windows = 3 x 1.5 m^2

= 4.5 m^2

Area to be white washed = Area of 4 walls – (Area of one door + Area of 3 windows)

Area to be white washed = [221 – (3 + 4.5)] m^2

= (221 – 7.5) m^2

= 213.5 m^2

We have cost of white washing for 1 m^2 area = Rs. 3.80

Cost of white washing for 213.5 m^2 area = Rs. (213.5 x 3.80)

= Rs. 811.30

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Question 20

A room is 9 m long, 8 m broad and 6.5 m high. It has one door of dimensions 2 m x 1.5 m and three windows each of dimensions 1.5 m x 1 m. Find the cost of white washing the walls at Rs 3.80 per square meter.

Looking to do well in your science exam ? Learn from an expert tutor. Book a free class!

Given Length of a room = 9 m

Breadth of a room = 8 m

Height of a room = 6.5 m

Area of 4 walls = 2(1 + b) h

= 2 (9 m + 8 m) x 6.5 m

= 2 x 17 m x 6.5 m

= 221 m^2

Length of a door = 2 m

Breadth of a door = 1.5 m

Area of a door = Length x Breadth

= 2 m x 1.5 m

= 3 m^2

Length of a window = 1.5 m

Breadth of a window = 1 m

Since, area of one window = Length x Breadth

= 1.5 m x 1 m

= 1.5 m^2

Thus, Area of 3 such windows = 3 x 1.5 m^2

= 4.5 m^2

Area to be white washed = Area of 4 walls – (Area of one door + Area of 3 windows)

Area to be white washed = [221 – (3 + 4.5)] m^2

= (221 – 7.5) m^2

= 213.5 m^2

We have cost of white washing for 1 m^2 area = Rs. 3.80

Cost of white washing for 213.5 m^2 area = Rs. (213.5 x 3.80)

= Rs. 811.30

Our top 5% students will be awarded a special scholarship to Lido.

subject-cta
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