\(t =\frac{ u \sin \theta}{ g }\)

\(\therefore \frac{ u _{1} \sin \theta_{1}}{ g }=\frac{ u _{2} \sin \theta_{2}}{ g }\)

\(\Rightarrow u _{1} \sin 30= u _{2} \sin 45\)

\(\Rightarrow \frac{ u _{1}}{ u _{2}}=\frac{1 / \sqrt{2}}{1 / 2}=\frac{\sqrt{2}}{1}\)