Postgres math expression calculcated for each row in table

Using PostgreSQL, supposing a table like the following:

 12184 |               4 |          83
 12183 |               3 |         171
 12176 |               6 |          95

How can I compute a math expression for each row in the table?

For example, to divide column 2 by column 3, such that the output would be:

 12184 |   0.04819277108
 12183 |   0.01754385965
 12176 |   0.06315789474

My instinct was to try:

SELECT col1, col2 / col3 FROM table_name;

But that return the ceiling (ie. rounded-down) integer part, I need the floating point value.