Question

The minute hand of a watch is $1.5cm$ long. How far does its tip move in $40$ minutes? (Use $\pi =3.14$)

• A. $2.68cm$
• B. $6.28cm$
• C. $6.82cm$
• D. $7.42cm$

Answer 1

Answer: (B)

In $60$ minutes, the minute hand of a watch completes one revolution. Therefore, in $40$ minutes, the minute hand turns through $\frac{2}{3}$ of a revolution. Therefore $\theta =\frac{2}{3}\times 360^{\circ }$ or $\frac{4\pi }{3}$ radian. Hence, the required distance travelled is given by
$l=r\theta =1.5\times \frac{4\pi }{3}$
$=2\pi =2\times 3.14=6.28cm$.