Whether calculating discount percent, sale price, original price, markup percent, or cost to store I have found that using percent proportions is the best way to do so. There are no decimal shifts (as there are when students use the percent equation, p = % • w) to cause errors, the amount of memorization is minimal ( the percent proportion, part/whole = percent/100, with some careful thinking before and/or after applying it, is all that is needed), and the problems can be solved relatively