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In a circle of radius $21$ cm, an arc subtends an angle of $60^{\circ}$ at the centre. Find the area of the sector formed by the arc. Also, find the length of the arc.
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$A = \frac{60}{360} \times \frac{22}{7} \times 21 \times 21 = 231 \text{ cm}^2$
Length of arc $= \frac{60}{360} \times 2 \times \frac{22}{7} \times 21 = 22 \text{ cm}$
Length of arc $= \frac{60}{360} \times 2 \times \frac{22}{7} \times 21 = 22 \text{ cm}$