Mathematics — Standard (041) — CBSE Class 10 board question

Using the formula: Length of arc $= \dfrac{\theta}{360} \times 2\pi r$

$10\pi = \dfrac{\theta}{360} \times 2\pi \times 12 \Rightarrow \theta = \dfrac{10\pi \times 360}{24\pi} = 150°$

Answer: (D) 150°

Apply the arc length formula directly. Cancel $\pi$ from both sides and solve for $\theta$. The key formula to remember is $l = \frac{\theta}{360} \times 2\pi r$ (from Summary point 1, Chapter 11).