Number Formatting

I have an excel spreadsheet, that is 11,000 lines (give or take) and in column A, I have a sequence of numbers on every line set up like this:

11-22-333-44W5

What I want to do is add the number "100/" to the begining of every number sequence. If I have to manually add it, I have to go down 11,000 Lines and add it to every line, is there a way to just tell excel to add the number "100/" and down fill it for everyline - end result will look like:

100/11-22-333-44W5