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Question
An open box is made of wood 3 cm thick. Its external length, breadth and height are 1.48 m, 1.16 m and 8.3 m. Find the cost of painting the inner surface of Rs 50 per sq. metre.
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Solution
Given
Length =1.48m=148cm.
Breath =1.16m =116 cm
Height = 8.3m = 83cm
Thickness of wood = 3cm
∴ inner dimensions:
Length (148 - 2 x 3)cm = 142cm
Breadth (116 - 2 x 3) cm = 110cm
Height= (83 - 3) cm = 80cm.
Inner surface area = 2 (l + b) + lb
`=2[(142)+100)80+142xx110cm^2]`
`2(252)[80]+142xx110cm^2=55,940cm^2`
`=559.40m^2`
Hence, cost of painting inner surface area
`=5,5940xxRs.50`
`=Rs.279.70`
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