Originally Posted by
Soroban Hello, neworld222!
I think it's Yoda, the Jedi Master . . .
I'll take a wild guess . . .
Ten distinct books are placed randomly on a shelf (in a row).
What is the probability that a particular five books are adjacent?
There are $\displaystyle 10!$ possible arrangements.
Duct-tape those five books together.
Then we have six "books" to arrange: .$\displaystyle \left\{\boxed{ABCDE},\,F,\,G,\,H,\,I,\,J\right\}$
. . They can be arranged in $\displaystyle 6!$ ways.
For each of these, the five books can be permuted in $\displaystyle 5!$ ways.
. . Hence, there are: .$\displaystyle (6!)(5!)$ desirable arrangements.
The probability is: .$\displaystyle \frac{(6!)(5!)}{10!} \;=\;\frac{1}{42}$