Calculate data and make it into new column using awk

[yat]

Hi everyone, just some simple question...

i've been using a awk script to calculate my data...

i have 3 files:

file a1.txt:
2
3
4
5
3
4

file a2.txt:
4
5
6
7
8

file a3.txt:
2
5
1
3
4

i successfully calculate the average of each file using awk:
awk '{ s += $1 } END { print s/NR }' a1.txt
awk '{ s += $1 } END { print s/NR }' a2.txt
awk '{ s += $1 } END { print s/NR }' a3.txt

the results were (3.5, 6 and 3) which is pretty easy..

now i want to combine all this into 1 file and each have different columns and called it avg.txt which have something like this in the end:

3.5 6 3

help is much appreciated, Tq

[Franklin52]

awk 'NR==1{s=$1; f=FILENAME; next}
f != FILENAME {a=a?a FS s/n:s/n ; f=FILENAME; s=0}
{s+=$1; n=FNR}
END{print a, s/n}' a1.txt a2.txt a3.txt