The dimensions of a room are (9m×8m×6.5m). It has one door of dimensions (2m×1.5m) and two windows each of dimensions (1.5m×1m).Find the cost of whitewashing the walls at Rs 6.40 per square metre.
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first we have to find surface area of all 4 walls
which is (lb+bh+hl)2
which comes out 2×(9×8+8×6.5+6.5×9)
2×(72+52.0+59.5)
2×(183.5)
367.0sq m
now will get the area of windows
2×(1.5×1)
3sq m
now door area
2×1.5
3sq m
will add door and windows area and subtract it from walls area
367.0-3+3
367.0-6
361.0sp m
will mutliply it with rate
361×6.4
2310.4rs
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Total surface area of the room=2(lh+lb+hb)m
2
=2[9×6.5+9×8+8×6.5]m
2
=365m
2
Area of the door =l×b=2×1.5=3m
2
Area of the windows=l×b=1.5×1=1.5m
2
∴ Surface area of walls=TSA of room −Area of door−Area of windows
=365−3−1.5=360.5m
2
Cost of whitewashing per square meter=Rs. 6.40
∴ Cost of whitewashing the walls=Rs. 6.40×360.5
=Rs. 2307.2.
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