[tex]Dane:\\s_1 = 1,5 \ km\\v_1 = 6\frac{km}{h}\\s_2 = 2 \ km\\v_2 = 4\frac{km}{h}\\s_3 = (5-3,5) \ km = 1,5 \ km\\Szukane:\\v_{sr} = ?\\\\Rozwiazanie\\\\v_{sr} = \frac{s_{c}}{t_{c}}\\\\s_{c} = 5 \ km\\\\t = \frac{s}{v}\\\\t_{c} = t_1+t_2+t_3\\\\t_{c} = \frac{s_1}{v_1} + \frac{s_2}{v_2} + \frac{s_3}{v_3} = \frac{1,5 \ km}{6\frac{km}{h}} + \frac{2 \ km}{4\frac{km}{h}}+ \frac{1,5 \ km}{5\frac{km}{h}}=(0,25+0,5+0,3) \ h =1,05 \ h[/tex]
[tex]v_{sr} = \frac{5 \ km}{1,05\frac{km}{h}}\\\\\boxed{v_{sr}\approx4,76\frac{km}{h}}[/tex]
Odp. Średnia prędkość Zuzi na trasie to ok. 4,76 km/h.
