Answer
5.03 cm
Work Step by Step
Radius $r=2.4\,cm$
Inorder to complete $360^{\circ}$ the minute hand takes 60 minutes.
Therefore in 20 minutes it covers an angle of $360^{\circ}\times\frac{20}{60}=120^{\circ}$.
That is, central angle $\theta=(120\times\frac{\pi}{180})\,radians=\frac{2\pi}{3}\,rad$
Arc length $s=r\times\theta=2.4\,cm\times\frac{2\pi}{3}=5.03\,cm$
