A body travels uniformly a distance of $\left(13.8 \pm 0.2\right)m$ in a time $\left(4.0 \pm 0.3\right) s$. Its velocity with error limits is

Here, $s=\left(13.8 \pm 0.2\right)m, t=\left(4.0 \pm 0.3\right) s$

$\therefore$ velocity, $v=\frac{s}{t}=\frac{13.8}{4.0}=3.45 m s^{-1}$

                                  (Rounded off to first place of decimal) 

$$\begin{gathered} \therefore \frac{△v}{v}=\frac{△s}{s}+\frac{△t}{t}=\frac{0.2}{13.8}+\frac{0.3}{4.0}=\frac{0.8+4.14}{13.8\times 4.0}=\frac{4.94}{13.8\times 4.0} \\ =0.0895 \end{gathered}$$

$or △v=v\times 0.0895=3.45\times 0.0895=0.3087$

$\therefore$ velocity $=\left(3.5 \pm 0.3\right) m s^{-1}$