Ola

$t_O=160\text{s}=\frac{160}{3600}\text{h}=\frac{2}{45}\text{h}$   - czas

$s=400\text{m}=0,4\text{km}=\frac{2}{5}\text{km}$   

Prędkość:

$v=\frac{s}{t}$  

$v_O=\frac{\frac{2}{5}\text{km}}{\frac{2}{45}\text{h}}=\frac{2}{5}\cdot \frac{45}{2}\frac{\text{km}}{\text{h}}=9\frac{\text{km}}{\text{h}}$      

 

Jacek

$t_J=100\text{s}=\frac{100}{3600}\text{h}=\frac{1}{36}\text{h}$    - czas

$s=400\text{m}=0,4\text{km}=\frac{2}{5}\text{km}$   

Prędkość:

$v=\frac{s}{t}$  

$v_J=\frac{\frac{2}{5}\text{km}}{\frac{1}{36}\text{h}}=\frac{2}{5}\cdot 36\frac{\text{km}}{\text{h}}=14,4\frac{\text{km}}{\text{h}}$  

 

Różnica prędkości:

$14,4-9=5,4\frac{\text{km}}{\text{h}}$  

 

Odp.: B