Respuesta :
Given:Three dice are tossed.
To find: Probability of rolling 3 different numbers.
Let E be the event of getting same number on three dice.
So,the favorable cases for E will be
(1,1,1) , (2,2,2) , (3,3,3), (4,4,4), (5,5,5) , (6,6,6).
So, the number of favorable cases=6
Now,the total number of cases for E will be
[tex]6\times6\times6[/tex]Since each dice has 6 numbers so three dice will have these number of cases.
Now, the probability to have a same number on 3 dice will be
[tex]P(E)=\frac{\text{Number of favorable cases}}{\text{Number of cases}}\text{ }[/tex][tex]\begin{gathered} P(E)=\frac{6}{6\times6\times6} \\ =\frac{1}{36} \end{gathered}[/tex]Now, probability of rolling 3 different numbers is
[tex]P(nu\text{mbers are different on thr}ee\text{ dice)}=1-P(E)[/tex][tex]\begin{gathered} =1-\frac{1}{36} \\ =\frac{30}{36} \\ =\frac{15}{18} \end{gathered}[/tex]Hence, the probability of rolling three different numbers is
[tex]\frac{15}{18}[/tex]