Numbers: divide in a column
The "spreadsheet" way to do this is to do the division in another column.

Lets say your data is column A, starts a row 1 and goes to row 10 (that's A1:A10 in spreadsheet reference language).

In a unused column, row 1, you could enter:

=A1/10


And the copy and paste that formula from row 2 down to rows 2 through 10 in that column. Numbers will automatically increment the A1 reference in the pasted cells.

The divisor (10 in this case) can also be a reference if you like. Just make it a fixed reference so it doesn't automatically increment as you copy and paste. Lets say B1 holds the value you want to divide everything in column A by. You'd use:

=A1/$B$1


as the formula and copy and paste. The $ in front of the column name and row number tell Numbers not to auto-adjust those values as you paste the formula around to different cells.

Here is an example Numbers '09 file.

Column A is data
Column B is A divided by 10
Column C is A divided by whatever value is in E2, change E2 and you'll see the values in Column C change.