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Question
The floor of a rectangular hall has a perimeter 250 m. If the cost of panting the four walls at the rate of Rs.10 per m2 is Rs.15000, find the height of the hall.
[Hint: Area of the four walls = Lateral surface area.]
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Solution
Let length, breadth, and height of the rectangular hall be l m, b m, and h m respectively.
Area of four walls = 2lh + 2bh
= 2(l + b) h
Perimeter of the floor of hall = 2(l + b)
= 250 m
∴ Area of four walls = 2(l + b) h = 250h m2
Cost of painting per m2 area = Rs 10
Cost of painting 250h m2 area = Rs (250h × 10) = Rs 2500h
However, it is given that the cost of paining the walls is Rs 15000.
∴ 15000 = 2500h
h = 6
Therefore, the height of the hall is 6 m.
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