A sector is cut from a circle of radius 21 cm with central angle $150^\circ$. What is the length of its arc? Take $\pi=\dfrac{22}{7}$.
A44 cm
B49 cm
C55 cm
D66 cm
Answer & Solution
Correct answer: C. 55 cm
Arc length of a sector is $l=\dfrac{\theta}{360}\cdot 2\pi r$. Substituting $\theta=150^\circ$ and $r=21$ cm gives $l=\dfrac{150}{360}\cdot 2\cdot\dfrac{22}{7}\cdot 21=55$ cm. Option D would correspond to taking too large a fraction of the full circumference.
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