The motion of the boat is basically a uniform motion on both directions, north-south (NS) and east-west (EW), with two constant velocities: [tex]v_{SN}=5.4~km/h[/tex] and [tex]v_{EW}=7.6~km/h[/tex].
From the law of motion on the EW direction we can find the total time of the motion:
[tex]S_{EW}(t) = v_{EW} t[/tex]
since we know [tex]S_{EW}=1.4~km[/tex], we find
[tex]t= \frac{S_{EW}}{v_{EW}} =0.18~h[/tex]
and then, we can find how far the boat went on the NS direction during this time:
[tex]S_{NS}=v_{NS} t =5.4~km/h \cdot 0.18~h = 1~km [/tex]
