The length, breadth and height of a cuboid are in the ratio 5 : 3 : 2 and its volume is 6480 cubic cm. What is its total surface area in square cm?

Let the edges be 5$k,3k$ and 2$k$. Then $30k^3=6480$, so $k^3=216$ and $k=6$, giving 30 cm, 18 cm and 12 cm. Total surface = $2(lb+bh+hl)=2(540+216+360)=2232$ sq cm. The trap 1116 forgets the factor 2; 4464 applies it twice; 1152 is the lateral surface $2h(l+b)=2\times 12\times 48$, the four walls with the top and bottom left out.