bonjour,
1/5 monte ds le 1er car, il reste 4/5 voyageurs
1/4 de 4/5 monte ds le 2eme car soit 4/20 =1/5
1/3 des autres, les autres = 1-(1/5+1/5) = 1-2/5 =(5-2)/5 =3/5
1/3*3/5 = 3/15 =1/5 monte ds le 3eme car
il reste 1-3(1/5) = 1-3/5 =(5-3)/5 = 2/5
1/2 de 2/5 monte ds le 4eme car = 2/5/(1/2) = 2/5*2/1 = 4/5
les derniers montent ds le 5eme car =
1-3(1/5)+4/5 =
1-(3/5+4/5) =
1-4/5 = (5-4)/5 = 1/5