An open box is made of wood 3 cm thick. Its external length, breadth and height are 1.48m, 1.16m and 8.3 dm.  Find the cost of painting the inner surface of Rs. 50 per sq. metre.

Explanation

as thickness`=0.03m`

so `l=1.48-0.06=1.42m`

`b=1.16-0.06=1.10`

`h=0.83-0.03=0.80`

so total inner surface area`=lb+2(bh+hl)`

`=1.42xx1.10+2(1.10xx0.80+0.80xx1.42)`

`=5.594m^2`

so total cost `=5.594xx50`

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