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 dm. Find the cost of painting the inner surface of Rs. 50per sq. metre.

Answer 1

Given,

Thickness of wood = 3cm

External length of box = 1.48 m = 148 cm

External breadth of box = 1.16 m = 116 cm

External height of box = 8.3 dm = 83 cm

So, inner dimensions of box = external dimension – thickness of wood

Inner length = 148- (2 × 3) = 142 cm

Inner breadth = 116 –(2 × 3) = 110 cm

Inner height = 83 - 3 = 80 cm

Hence , inner surface area of box = lateral surface area +area of roof =2(l + b)h + l × b

= 2 (142 + 110)83 + 142 × 110

= 55940 cm² = 5.5940 m² 

∴ cost of painting at rate Rs.50 per m² = 50 × 5.5940 = Rs. 279.70