An arc of a circle subtends an angle of 30° on the circumference of a circle of radius 21cm. Find the length of the arc.

  • A 11cm
  • B 22cm
  • C 44cm
  • D 66cm
jamb 2003mathematics

The correct answer is B. 22cm

θ = 30 x 2(∠ at center twice ∠ at θ)

∴ θ = 60°

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

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

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