Formatting ratio formula results

Probably.

What's your formula?

Maybe something like this?

=TEXT(A1/B1,".#")&":1"

or this:

=ROUND(A1/B1,1)&":1"

or go to the cell properties and format as custom (by typing .# into the bar on the custom tab)

Where A1 and B1 are the two numbers being divided to achieve the ratio.