Ubuntu :: Calculate An Average In A Simple Way With Bash?

does anyone know how to calculate an average in a simple way with bash? I've got something like this:

Code:
$ cat results.txt | head -10 | tr " " " " | cut -f13
0.23929285124
0.404716908011
0.35113102608

[Code]....

and now I want to calculate the average of the resulting numbers. I know I could write a bash or awk or perl script and use that, but isn't there a more simple, elegant way? There is for example "sum" in the coreutils, but no "avg"..