A car has two wipers which do not overlap. Each wiper has a blade of length $\displaystyle 21$ cm sweeping through an angle of $\displaystyle 120$°. Find the total area cleaned at each sweep of the two blades.

\[\begin{aligned} & \text { Area cleaned by 1 blade }=\frac{22}{7} \times 21 \times 21 \times \frac{120^{\circ}}{360^{\circ}} \\ & \qquad=462 \\ & \begin{aligned} & \text { ⇒ Total area cleaned }= 2 \times 462=924 \\ & \therefore \text { Total area cleaned is } 924 \mathrm{~cm}^{2} \end{aligned} \end{aligned} \]