Permutations formula
[tex]_nP_r=\frac{n!}{(n-r)!}[/tex]where n things are chosen r at a time.
In this case, we need to find the number of permutations of n = 5 students chosen r = 5 at a time. That is,
[tex]\begin{gathered} _5P_5=\frac{5!}{(5-5)!} \\ _5P_5=\frac{5!}{0!} \\ _5P_5=\frac{5\cdot4\cdot3\cdot2\cdot1}{1} \\ _5P_5=120 \end{gathered}[/tex]They can stand in line in 120 different ways
