A rectangle 7 cm by 12 cm is spun once about its 12 cm side. Find the volume of the solid formed, in ${\text{cm}}^3$. Take π = 22/7.

The solid is a cylinder whose radius is the 7 cm side swung round and whose height is the 12 cm axis. Volume = $(22/7)\times 49\times 12=1848{\text{cm}}^3$. (Spinning about the 7 cm side instead would give radius 12 cm and height 7 cm, a volume of $3168{\text{cm}}^3$; using the cone formula gives $616{\text{cm}}^3.$)