Question

A class room is 7 m long, 6.5 metres wide and 4 m high. It has one door 3 m. × 1.4 m and three windows, each measuring 2 m × 1 m. The interior wall are able to be colour washed. The contractor charge 5.25 Rs per sq. m. Find the cost of colur washing.​

Answer 1

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

=(2x4(7+6.5))

=(8x13. 5)

=108m square

area of one window =3mx1. 4m

=4.2m square

area of three window =3(2mx1m)

=6m square

total area of windows =(4.2+6)m square

=10.2m square

Area for whitewashing =(108-10.2)m square

=97.8m square

cost of 1 m square white washing = 3.50rupee

cost of 97.8m square white washing=3.50x97.8

=342.3 rupees

Answer 2

Given:

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• Length (l) = 7 m
• Breadth (b) = 6.5 m
• Height (h) = 4 m

It has one door with length of 3 m and breadth of 1.4 m and three windows, each measuring 2 m × 1 m.

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The contractor charges 5.25 Rs per square metre white washing.

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To find:

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Cost of colour washing of the interior wall are to be colour washed.

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Solution:

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Area of the four walls without any gap will be

2( l + b )h

[since lateral surface area of cuboid = 2( l + b )h]

Area of the door = l × b

= 3 × 1.4 m$^{2}$

= 4.2 m$^{2}$

Area of a window = l × b

= 2 × 1 m$^{2}$

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So, area of three windows = 3 × (2 × 1)m$^{2}$ = 6m$^{2}$

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Hence, area to be colour washed = Area of the four walls inclusive of doors and windows – (area of the door + area of the three windows)

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= {108 – (42 + 1)}

= 97.8 m$^{2}$

So, cost of colour washing

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= 97.8 × 5.25

= 513.45 Rs