An open tin box, 21 cm long, 9 cm wide, 8 cm high, is fitted with a thin lid which overlaps to a depth of 1 cm all round. What is the total area of tin sheeting used for the box and the lid?

The area for the open box is (21+21+9+9)*8 + (21*9) = 669 cm

^{2}The area for the lid will be (21+21+9+9)*1 + (21*9) = 249 cm

^{2}Total area = 918 cm

^{2}