Question

A box with out upper lid is made of wood of width 3 cm. Its external length, breadth and height are 146 cm, 116 cm and 83 cm respectively. Find cost of painting inside if the rate of painting = Rs 2 per 1000 sq.cm.

Answer 1

The external length of box = 146 cm

breadth = 116 cm

height = 83 cm

The width of the wood = 3 cm

∴ The internal length of box 

= (146 – 3 – 3) = 140 cm.

Internal breadth of box 

= (116 – 3 – 3) = 110 cm

Internal height of box = 83 – 3 = 80 cm.

Besides of the lid, the internal total surface area of the box

= 2(l + b) × h + l × b

= 2(140 + 110) × 80 + (140 × 110)

= 160 × 250 + 15400

= 55400 sq. cm.

The cost of painting of 1000 sq. cm. = Rs 2.

∴ The cost of painting of 55400 = \(\frac { 2\times 55400 }{ 1000 } \) = Rs 110.80

Hence the cost of painting the box = Rs 110.80.