S1=10m U1=20cm/cek S2=30m t2=1min Uср. -?
Uср.=S/t
S=S₁+S₂=10m+30m=40m
t₁=S₁/U₁=10m/0,2m/c=50c
t=t₁+t₂=50c+60c=110c
Uср.=40m/210c=0,364m/c