How can I make sub-columns width expand to their parent width?

I have my example here:

http://jsfiddle开发者_运维百科.net/bfYFq/

Column1 through Column3 divs use up 100% of their parent containers space evenly. I want the sub columns (sub1, sub2 and sub3) to do the same instead of just being the length of their text. How can I accomplish this?

Try this: http://jsfiddle.net/bfYFq/2/

Note second selector.