Below are links to tutorials on youtube for finding percent of a number

http://www.youtube.com/watch?v=32_Q3bayRps - using the 10% benchmark

http://www.youtube.com/watch?v=SOOK094MmDs - finding percent of a number

http://www.youtube.com/watch?v=AIoTux8l8R4 - finding the number of by dividing

http://www.youtube.com/watch?v=V7UF0hE7AQY - using is/of=%/100