A car has two wipers which do not overlap. Each wiper has a blade of length 28 cm and sweeps through an angle of 120°. Find the total area cleaned at each sweep of the blades.                                                          [Page No. 148]

Area swept by one wiper = $\pi r^2 \times \frac{\theta}{360^\circ}$

$$\begin{aligned} &= \frac{22}{7} \times 28^2 \times \frac{120}{360} \\ &= \frac{22}{7} \times 784 \times \frac{1}{3} \\ &= \frac{22 \times 784}{21} = \frac{17248}{21} = 821.33 \text{ cm}^2 \\ &= 2 \times 821.33 \\ &= 1642.67 \text{ cm}^2 \end{aligned}$$