The minute hand of a clock is 21 cm long. Find the area, in ${\text{cm}}^2$, that it sweeps over in 5 minutes. Take π = 22/7.

In 5 minutes the hand turns through 5/60 = 1/12 of a full turn, that is 30°. Area = $(1/12)\times (22/7)\times 21^2=(1/12)\times 1386=115.5{\text{cm}}^2.(1386{\text{cm}}^2$ is what it sweeps in a whole hour; 11 cm is how far the tip travels, a length not an area.)