A solid block of wax measuring 18 cm × 12 cm × 8 cm is melted and recast as a single cube. Find the edge of that cube.

Melting keeps the volume the same: $18\times 12\times 8=1728{\text{cm}}^3$. For the cube, $s^3=1728$ → $s=12$ cm $(12\times 12\times 12=1728)$. Trap 1728 cm: reporting the volume as if it were a length. Trap 576 cm: dividing 1728 by 3 instead of taking the cube root. Trap 24 cm: doubling the correct edge.