$v=\frac{\text { Distance }}{\text { Time taken }}$
As shown in given figure
$\frac{v_{1}}{v_{2}}=\frac{\frac{s_{0}}{t_{1}}}{\frac{s_{0}}{t_{2}}}=\frac{s_{0}}{t_{1}} \times \frac{t_{2}}{s_{0}}$
$\frac{v_{1}}{v_{2}}=\frac{4}{2}=\frac{2}{1}$
Therefore, the ratio of speeds is
$v_{1}: v_{2}=2: 1$
