It's pretty simple actually, it's least to greatest? Then lets start out with the least, which means closest to 0:
1.2
1.23
Since 1.23 has more numbers in it, it is greater than 1.2, because 1.2 could also be written out as 1.20 and that is less than 1.23.
Now lets go with the greatest:
2.31
3.2
It's obvious 3.2 would be the greatest, so therefore:
1.2, 1.23, 2.31, 3.2
is from least to greatest.
Hope this helps!
