A channel of width $450$ $mm$ branches into two sub-channels having width $300$ $mm$ and $200$ $mm$ as shown in figure. If the volumetric flow rate (taking unit depth) of an incompressible flow through the main channel is $0.9$ $m^3/s$ and the velocity in the sub-channel of width $200$ $mm$ is $3$ $m/s$, the velocity in the sub-channel of width $300$ $mm$ is _____________ $m/s$.
Assume both inlet and outlet to be at the same elevation.
