<HTML><BODY style="word-wrap: break-word; -khtml-nbsp-mode: space; -khtml-line-break: after-white-space; "><DIV><BLOCKQUOTE type="cite"> </BLOCKQUOTE></DIV> The problem here is that we all agree (more or less) on the definition of % (i.e. 15%=0.15), but there seems to be disagreement on the "+". My take is that if you write out the equation (as the OP did), 28.05+15%=X, then the correct answer is that X=28.2, since the "+" separates the original number and the %. We don't, in standard mathematical notation, have an operator that says "increase by X%"; many calculators have therefor adopted the convention of Y+n%=Y*(1+n/100). However, this is strictly a calculator convention, and does not strictly correspond to the written equation form of the calculation, as noted above. In Excel, for instance, where you actually type the equation, it gives 28.20 as the (correct) answer, yet on the calculator on my Palm, it gives 30.3.<DIV><DIV> I think that a calculator should probably work the latter way, for convenience, in spite of the fact that it does not follow the written equation form. However, this causes problems when you use a slightly more complex formula. For example, 28.05+15%*1 produces 30.3 using this convention, when a strict adhesion to mathematical rules says that the "*" takes precedence over the "+", and therefore the 15% should be of the 1, not the 28.05. The answer in this case is definitively 28.2, yet the calculator gets it wrong.</DIV><DIV> Who knew a "+" could be so much trouble?</DIV><DIV><BR><DIV> <P style="margin: 0.0px 0.0px 0.0px 0.0px"><FONT face="Helvetica" size="3" style="font: 12.0px Helvetica">Aron S. Spencer, Ph.D.</FONT></P> <P style="margin: 0.0px 0.0px 0.0px 0.0px"><FONT face="Helvetica" size="3" style="font: 12.0px Helvetica">Assistant Professor</FONT></P> <P style="margin: 0.0px 0.0px 0.0px 0.0px"><FONT face="Helvetica" size="3" style="font: 12.0px Helvetica">New Jersey Institute of Technology</FONT></P> <P style="margin: 0.0px 0.0px 0.0px 0.0px"><FONT face="Helvetica" size="3" style="font: 12.0px Helvetica">Newark, NJ 07102</FONT></P> </DIV><BR></DIV></DIV></BODY></HTML>