Bonsoir,
[tex]Soit\ d\ la\ longueur\ de\ la\ mont\' ee}\\v_1,t_1\ la\ vitesse\ et\ le\ temps\ de\ la\ mont\' ee\\v_2,t_2\ la\ vitesse\ et\ le\ temps\ de\ la\ descente\\\\d=v_1*t_1\\d=v_2*t_2\\2d=v*(t_1+t_2)\\\\\dfrac{d}{v_1} +\dfrac{d}{v_2} =\dfrac{2d}{v} \\\\\boxed{v=\dfrac{2*v_1*v_2}{v_1+v_2} }\\\\\\v=\dfrac{2*17*33}{17+33} =\dfrac{1122}{50}= 22,44(km/h)[/tex]
