Two solid cubes of edge 4 cm are glued together face to face to form a single cuboid. Find the total surface area of that cuboid in ${\text{cm}}^2$.

The cuboid measures 8 cm by 4 cm by 4 cm, so its surface = $2(8\times 4+4\times 4+8\times 4)=2(32+16+32)=160{\text{cm}}^2$. Checking the other way: the two cubes showed $2\times 96=192{\text{cm}}^2$, and gluing hides one $16{\text{cm}}^2$ face on each, so $192-32=160{\text{cm}}^2.(192{\text{cm}}^2$ keeps them apart; $128{\text{cm}}^2$ takes away $64{\text{cm}}^2$, as if four faces vanished instead of two; $96{\text{cm}}^2$ is a single cube.)