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**A lane 180 m long and 5 m wide is to be paved with bricks of length 20 cm and breadth 15 cm. Find the cost of bricks that are required, at the rate of Rs 750 per thousand.**

We have,

Length of the lane = 180 m

Breadth of the lane = 5 m

Area of a lane = Length x Breadth = 180 m x 5 m = 900 m^{2}

Length of the brick = 20 cm

Breadth of the brick = 15 cm

Area of a brick = Length x Breadth = 20 cm x 15 cm = 300 cm^{2} = 0.03 m^{2} [Since 1 m^{2} = 10000 cm^{2} ]

Required number of bricks =

Cost of 1000 bricks = Rs. 750

âˆ´ Total cost of 30,000 bricks = Rs.

**How many envelopes can be made out of a sheet of paper 125 cm by 85 cm; supposing one envelope requires a piece of paper of size 17 cm by 5 cm?**

We have,

Length of the sheet of paper = 125 cm

Breadth of the sheet of paper = 85 cm

Area of a sheet of paper = Length x Breadth = 125 cm x 85 cm = 10,625 cm^{2}

Length of sheet required for an envelope = 17 cm

Breadth of sheet required for an envelope = 5 cm

Area of the sheet required for one envelope = Length x Breadth = 17 cm x 5 cm = 85 cm^{2}

Thus,

Required number of envelopes =

**The width of a cloth is 170 cm. Calculate the length of the cloth required to make 25 diapers, if each diaper requires a piece of cloth of size 50 cm by 17 cm.**

We have,

Length of the diaper = 50 cm

Breadth of the diaper = 17 cm

Area of cloth to make 1 diaper = Length x Breadth = 50 cm x 17 cm = 850 cm^{2}

Thus,

Area of 25 such diapers = (25 x 850) cm^{2} = 21,250 cm^{2}

Area of total cloth = Area of 25 diapers

= 21,250 cm^{2}

It is given that width of a cloth = 170 cm

âˆ´ Length of the cloth =

Hence, length of the cloth will be 125 cm.

**The carpet for a room 6.6 m by 5.6 m costs Rs 3960 and it was made from a roll 70 cm wide. Find the cost of the carpet per metro.**

We have,

Length of a room = 6.6 m

Breadth of a room = 5.6 m

Area of a room = Length x Breadth = 6.6 m x 5.6 m = 36.96 m^{2}

Width of a carpet = 70 cm = 0.7 m [Since 1 m = 100 cm]

Length of a carpet =

Cost of 52.8 m long roll of carpet = Rs. 3960

Therefore,

Cost of 1 m long roll of carpet = Rs. 3960/52.8= Rs. 75

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

We have,

Length of a room = 9 m

Breadth of a room = 8 m

Height of a room = 6.5 m

Area of 4 walls = 2(l + 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 âˆ’ (Area of one door + Area of 3 windows)

Area to be white-washed = [221 âˆ’ (3 + 4.5^{ })] m^{2}

= (221 âˆ’ 7.5 ) m^{2} = 213.5 m^{2}

Cost of white-washing for 1 m^{2} area = Rs. 3.80

âˆ´ Cost of white-washing for 213.5 m^{2} area = Rs. (213.5 x 3.80) = Rs. 811.30

**A hall 36 m long and 24 m broad allowing 80 m ^{2} for doors and windows, the cost of papering the walls at Rs 8.40 per m^{2} is Rs 9408. Find the height of the hall.**

We have,

Length of the hall = 36 m

Breadth of the hall = 24 m

Let h be the height of the hall.

Now, in papering the wall, we need to paper the four walls excluding the floor and roof of the hall.

So, the area of the wall which is to be papered = Area of 4 walls

= 2h(l + b)

= 2h (36 + 24) = 120h m^{2}

Now, area left for the door and the windows = 80 m^{2}

So, the area which is actually papered = (120h âˆ’ 80) m^{2}

Again,

The cost of papering the walls at Rs 8.40 per m^{2} = Rs. 9408.

â‡’ (120h âˆ’ 80) m^{2} x Rs. 8.40 per m^{2}^{ }= Rs. 9408

â‡’ (120h* *âˆ’ 80) m^{2} =

â‡’ (120h âˆ’ 80) m^{2} = 1120 m^{2}

â‡’ 120h* *m^{2} = (1120 + 80) m^{2}

â‡’ 120h* *m^{2}^{ }= 1200 m^{2}

Hence, the height of the wall would be 10 m.