An arc of a circle subtends an angle of 30^\circ on the circumference of a circle of radius 21cm. Find the length of the arc.
A
11cm
B
22cm
C
44cm
D
66cm
Verified Correct Answer: B.
Step-by-Step Mathematical Solution
\theta = 30 x 2(∠ at center twice ∠ at circumference)
∴ \theta = 60^\circ
Length of arc = \(\frac{\theta}{360}\times 2\pi r\)
= \(\frac{60}{360}\times 2 \times \frac{22}{7}\times \frac{21}{1}\)
= 22cm
Source: Myschool Past Questions Archive (Record #11104)