Question

The minute hand of a clock is 10 cm long. How far does the tip of the hand move in 20 minutes

• A. $\frac{3}{20}cm$
• B. $\frac{3\pi }{20}cm$
• C. $\frac{20}{3}cm$
• D. $\frac{20\pi }{3}cm$

Answer 1

Answer: (D)

Angle moved in 20 minutes = $120^{\circ }=\frac{2\pi }{3}$
Here r = 10 cm , Use $\theta =\frac{l}{r}$
$\Rightarrow$ $l=r\theta =10\left(\frac{2\pi }{3}\right)=\frac{20\pi }{3}$