Question

Find the length of the arc of a circle of diameter 42 cm which subtends an angle of 60° at the centre. [CBSE 2012]

Answer 1

We have $r=\frac{\mathrm{diameter}}{2}=\frac{42}{2}=21\mathrm{cm}\mathrm{and}\mathrm{\theta }=60°$
Length of arc = $\frac{\mathrm{\theta }}{{360}^{°}}\times 2\mathrm{\pi }r=\frac{60°}{360°}\times 2\times \frac{22}{7}\times 21=22\mathrm{cm}$
Hence, the length of the arc of the circle is 22 cm.