Question 3
A microgroove rotates at speed of $33 \frac{1}{3}$ revolutions per minute and its hearing lasts 24 min $30 \mathrm{~s}$. The engraved part has an outer diameter $29 \mathrm{~cm}$ and 11.5 $\mathrm{cm}$ inner diameter. With these data, calculate the length of the engraved groove.