[tex]21 \frac{km}{h} ~~\Rightarrow ~~21~km=21~000~m~~pokona~~ w~~1~h=3~600~s\\\\21~000~m~~~~---------------3~600~s\\~~~~200~m~~~~---------------~~x\\\\x=\dfrac{ 200~m \cdot 3~600~s }{ 21~000~m } \\\\x=\dfrac{720~000}{21~000} [s]\\\\x=34,2857~[s]\\\\x\approx 34,29~[s][/tex]
