Elements with r-th roots in finite groups

The probability that a randomly chosen element of a finite group is an $r$--th root (for any integer $r\geq2$) has been studied largely in case $r=2$. Certain techniques may be generalized for $r>2$ and here we find the exact value of this probability for projective special linear groups. A result of density is placed at the end, in order to show an analogy with the case $r=2$.