From the way you worded your question it doesn't look to me like you want to "work a percent backwards". If the number is 100 you know that 100% of 100 is 100 (or 100 "individual percents").
If you move the decimal point (that you can't see but know is there) over one place toward your left hand, you'll see what 10% is (but you don't want that).
If you move the decimal point over two places toward your left hand, you'll see what 1% is (and that's what you want to start with).
Here's what 100 would look like if the decimal point were written: 100. (and there may be a zero or two after it - or not). Here's what moving it one place toward your left would turn it into 10.0. Here's what happens if you move the decimal point twice toward your left to get 1%: 1.00
So now you know that 1% is 1. If you want 7, 8, or whatever other simple percent like that; all you have to do is multiply the 1 (1 percent) by the 7, 8, or whatever other number you want.
With 7 times the 1 (1%) you easily know that 7 x 1 is 7 (and you've got your 7% of 100).
Hope this helps, and hope I understood the question correctly.
100% of any number always refers to how big 100 equal little parts of anything/any number would be if you divided it up into that 100 equal little parts.
A single percent is always 1%, and figuring out 1% is easy to do by moving the decimal point over two places toward your left. That's why it can come in handy to figure out the 1% first, and then just multiply that by whatever "number percent" you need to find.