Question

A minute hand of a clock is $9 cm$ 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 $=9 cm$
and area $=\theta \times \underline{r}$
$=\frac{2 \pi}{3} \times 9=6 \pi$