`a,` $\delta t = \dfrac{\Delta t}{\bar{t}} \cdot 100\% = \dfrac{0,015}{2,540} \cdot 100\% \approx 0,59\%$

`b,` $\bar{v} = \dfrac{\bar{s}}{\bar{t}} = \dfrac{120,00}{2,540} \approx 47,24 \text{ cm/s}$

$\delta s = \dfrac{\Delta s}{\bar{s}} \cdot 100\% = \dfrac{0,50}{120,00} \cdot 100\% \approx 0,42\%$

$\delta v = \delta s + \delta t = 0,42\% + 0,59\% = 1,01\%$

$\Delta v = \bar{v} \cdot \delta v = 47,24 \cdot 1,01\% \approx 0,48 \text{ cm/s}$

$v = \bar{v} \pm \Delta v = (47,24 \pm 0,48) \text{ cm/s}$