A chocolate box is a prism 25 cm long whose two ends are equilateral triangles of side 6 cm. What is the total area of card used to make it, in square cm? (Take √3 = 1.73.)

The three long faces are rectangles 6 cm by 25 cm, giving $3\times 150=450$ sq cm. Each triangular end is (√3/4) $x{6}^2=(1.73/4)\times 36=15.57$ sq cm, and there are two, adding 31.14 sq cm. Total = 481.14 sq cm. The trap 450 makes an open tube with no ends; 465.57 closes only one end; 512.28 uses (√3/2)$a^2=31.14$ for each end, doubling the correct triangle area.