Question

A minute hand of a clock is $9cm$ long. How for does the tip of a hand move in 20 minutes?

• A. $8\pi$
• B. $6\pi$
• C. $\frac{18}{5}\pi$
• D. $\frac{20}{3}\pi$

Answer 1

Answer: (B)

Angle moves in 1 minutes $=6^{\circ }$
So, angle moves in 20 minutes $=6\times 20=120^{\circ }$
$=120^{\circ }=\frac{2\pi }{3}$
Here radius $=9cm$
and area $=\theta \times \underline{r}$
$=\frac{2\pi }{3}\times 9=6\pi$