Whether doing discount percent, markup percent, percent of change (increase or decrease), or tax and tip problems, all of which involve percent calculations, 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