Obtaining percentages from channel entriesing percentages from channel entries

I have built a customer survey for a client, just a SafeCracker form. They are wanting to have a simple stats page that shows some information about surveys that have been submitted.

An example: What percentage of respondents gave us a 5 rating?

This will tell me how many surveys have a 5 rating:

{exp:query sql="SELECT * FROM  `exp_channel_data` WHERE `channel_id` = '14' AND `field_id_30` = '5'"}{if count == total_results}{total_results}{/if}{/exp:query}

And this will tell me how many surveys have been taken:

{exp:stats channel="survey"}{total_entries}{/exp:stats}

So I have the 2 numbers I need to do the math, I just can’t make it process right. I have tried the exp:math plugin on devot:ee but I can’t make it work, probably because of parse order.

Does anybody have an suggestions? Thanks!

Jonathan