The probability is 12/194580
Explanation:The balls numbered 1 through 12 are:
1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12
1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12
1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12
1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12
If 4 balls have the same number, then there are 12 types of this arrangement:
1, 1, 1, 1
2, 2, 2, 2
3, 3, 3, 3
and so on.
There is also 4 * 12 = 48 total number of balls.
We have a permutation:
[tex]\begin{gathered} 48C4=\frac{48!}{(48-4)!4!} \\ \\ =\frac{48!}{44!4!}=194580 \end{gathered}[/tex]Finally, we
[tex]\frac{12}{194580}[/tex]This is the required probability.