Răspuns:
Explicație pas cu pas:
Toatal bile: 5a+3n+1r=9 bile
a) extragerea a 4 bile albe
prima extragere =5/9
a doua extragere=4/8=1/2
a treia extragere=3/7
a patra extragere=2/6=1/3
probabilitatea A=5/9×1/2×3/7×1/3=5/126≅0,04
prpbabilitatea B=A×1/5=5/126×1/5=1/126
C=5/9×4/8×3/7×1/6=5/9×1/2×1/7×1/2=5/252
D=1