
Originally Posted by
Soroban
Hello, sunrise2007!
Your denominator is correct.
. . There are: .$\displaystyle 5^4 \:= \:{\color{red}625}$ possible assignments.
Two students will be assigned the same section.
. . There are: .$\displaystyle {4\choose2} = {\color{blue}6}$ ways to choose the two students.
. . They can be assigned to any of the 5 sections.
. . The other two students have: .$\displaystyle 4 \times 3 \:=\:{\color{blue}12}$ possible assignments.
Hence, there are: .$\displaystyle 6 \times 5 \times 12 \:=\:{\color{red}360}$ ways.
Therefore, the probability is: .$\displaystyle \frac{360}{625} \;=\;\boxed{\frac{72}{125}}$
your answer Mr.Soroban very logic
my answer was correct but it is mising the permutition of two student and how are the student that choosen from the group ,
is describtion correct ???
Thank you so much for every one....
sorry ,i have another problem 
the problem is
If P (A1) = 5 P (A2) , AC S.
P(A/A1)= 0.2 ,P(A/A2) = 0.3
what is the value of P (A1 /A) ?
i am trying to solve it but i can not find the relation between the rules...
From the rules
P(A/A2)=P(A ∩A2)/P(A2)
0.3= P(A ∩A2)/P(A2)
P(A/A1)=P(A ∩A1)/P(A1)
0.2= P(A ∩A1)/P(A1)
= P(A ∩A1)/ 5 P(A2)