An arc of a circle subtends an angle of 30o on ... - JAMB Mathematics 2003 Question

θ = 30 x 2(∠ at center twice ∠ at θ)

∴ θ = 60^o

Length of arc = (\frac{\theta}{360}\times 2\pi r\

=\frac{60}{360}\times 2 \times \frac{22}{7}\times \frac{21}{1}\

=22cm)