Question

Find the cost of painting the all round outer surface of a box with lid 60 cm long, 40 cm wide and 30 cm high at 50p per 20 cm²?

Answer 1

Total surface area of the box = 2(lb+bh+hl)
Here, l = 60 cm, b = 40 cm and h = 30 cm.
Hence, total surface area of the box = 2(60×40+40×30+30×60) = 2(2400+1200+1800) = 10800 cm²
Cost of painting 20 cm² area = Rs. 0.5
Cost of painting 1 cm² area = Rs. 0.5/20 = Rs 0.025
Total cost = 0.025×10800 = Rs. 270