2/5 goes two-fifths of the way from 0 going toward 1.
It's where the "☻" is below:

-------------☻-------------
-2   -1    0    1    2    3

In cases of fractions, unless you have very accurate 
measuring tools you'll just have to guess about how far
a fraction is between two integers.  You'd usually ask
yourself "Is it more or less than half-way?" In the above 
you'd just guess that 2/5 is a little less than half way 
between 0 and 1.  If you have 5 marks between the integers
as above, you can get it accurately. But normally it doesn't 
matter if you just guess it fairly close.

Edwin