v₁=12 km/h=3,33 m/s
v₂=24 km/h=6,66 m/s
v₃=48 km/h=13,33 m/s
t₁=2 min=120 s
t₂=6 min=360 s
t₃=t₁=2 min=120 s
d₁=v₁t₁=3,33*120=399,6 m
d₂=v₂t₂=6,66*360=2397,6 m
d₃=v₃t₃=13,33*120=1599,6 m
d=d₁+d₂+d₃=399,6+1599,6+2397,6=4396,8 m
t=t₁+t₂+t₃=120+360+120=600 s
vm=d/t=4396,8/600=7,32 m/s