100% of something is all of it, exactly one of it. Example 100% of 6 = 1.00*6 = 6 If you are starting with some fraction and you want to find the whole amount, you can divide what you have by the fraction that you have. Example 170 = 85% of (what?) 170/85% = (what?) (divide both sides by 85%. Remember "of" means "times".) 200 = (what?) (this is 100% of "what?") You know that 100% = 1, so 1% = 1/100 = 0.01 (move the decimal point and drop the % sign to convert to decimal from percent)