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.

Answer 1

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`