Trying to get printf to do something

Hi PHP List Members, I work for Northern Michigan University. Currently I am a student studying accounting. In any case, I'm developing a survey for the Auxiliary service department. My Problem: The idea goes like this. S= total people satisfied with dining services N= total number of respondents S / N = some number less than one (eg., .87) I would like to use a function to alter that decimal number to a percentage. However I haven't had much luck. If you could please help, I'd be very relieved and appreciative for your services! I've tried the printf function but haven't had much luck. Thank You Much! Zach Korpi