Question

The large hand of a clock is $42cm$ long. How much distance does its extremity move in $20$ minutes?

• A. 88 cm
• B. 80 cm
• C. 75 cm
• D. 77 cm

Answer 1

Answer: (A)

The large hand of the clock makes a complete revolution in $60$ minutes.
$\therefore$ Angle traced out by the large hand in $20$ minutes
$($ of time $)=\frac{360^{\circ }\times 20}{60}=120^{\circ }=\frac{2\pi }{3}$ radian
Hence, the distance moved by the extremity of the large $=(42)\times \frac{2\pi }{3}=88cm$.
$(\because l=r\theta )$