Odpowiedź :
t1=10 min = 1/6 h
s1 =30 km
v2 = 80 km/h
s2=20 km
t3=(1/4) h
V3= 40 km/h
Vśr = s/t
s=s1+s2+s3
t=t1+t2+t3
V2=s2/t2
t2=s2/V2
s3=V3*t3
Vśr=(s1+s2+V3*t3)/(t1+s2/V2+t3)
Vśr=(30+20+40*0,25)/(1/6+20/80+1/4)
Vśr= 90 km/h
t1=10 min = 1/6 h
s1 =30 km
v2 = 80 km/h
s2=20 km
t3=(1/4) h
V3= 40 km/h
Vśr = s/t
s=s1+s2+s3
t=t1+t2+t3
V2=s2/t2
t2=s2/V2
s3=V3*t3
Vśr=(s1+s2+V3*t3)/(t1+s2/V2+t3)
Vśr=(30+20+40*0,25)/(1/6+20/80+1/4)
Vśr= 90 km/h