[X4U] Tiger's Calculator.app no longer does percentages?

[Aron Spencer]

    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.
    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.
    Who knew a "+" could be so much trouble?

Aron S. Spencer, Ph.D.
Assistant Professor
New Jersey Institute of Technology
Newark, NJ 07102

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