Sagot :
1) arbre pondéré :
- niveau 1:
--------> V(3/4)
--------> R(1/4)
- niveau 2 :
V(3/4) --------> V(1/3)
--------> R(2/3)
R(1/4) --------> V(1/3)
--------> R(2/3)
2) a) P(VR)=3/4*2/3
=6/12
=1/2
b) P(VV)+P(RR)
=3/4*1/3+1/4*2/3
=3/12+2/12
=5/12
c) p=1-P(VV)
=1-3/4*1/3
=1-1/4
=3/4