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

[John Baltutis]

On 11/26/05, Neil <Lists at mac.com> wrote:
> on 11/26/05 6:07 PM, John Baltutis wrote:
>
>> Color me confused, but 15% = 0.15, which when added to 28.05 = 28.2 (at
>> least that's consistent with what I learned in school 58 years ago). To do
>> what you want, simply use 28.05 * 1.15 = 32.2575.
>
> The reason your are confused is because "15% of" is the same thing as "0.15
> times,"  but the only time 15%=0.15 is when it is 15% of 1.0.

Really? 15%, by definition, is 15/100 = 0.15. See
<http://www.mathleague.com/help/percent/percent.htm>,
<http://www.math.com/school/subject1/lessons/S1U1L7GL.html>, and
<http://www.purplemath.com/modules/percents.htm>.

> When your dinner bill comes to $127 do you leave a dime and
>  a nickel as a 15% tip (ie. $.15)?

No. I leave the original amount plus 15% of it; i.e., 127 + 127 x 0.15 =
127 x 1.15 = 146.05.

> I think the original example is ambiguous because it didn't specify the
> "of."  One very reasonable assumption would be that the 15% mentioned in the
> equation is 15% of the 28.05.

Unambiguous and unreasonable in any mathematical sense. The original
problem was the sum of two numbers: 28.05 + 15% = 28.2, which is
mathematically correct.

> I'm not sure that I would consider a calculator broken just because it
> didn't make that assumption, but it makes no sense at all for the calculator
> to assume that it's 15% of 1. Where did the 1 come from?  Thin air?

As before, from the standard mathematical definition of the term percent.

>> If Panther's calculator works the way you described, then, IMHO, it's the
>> one with the error, not the one in Tiger.
>
> I disagree.  Panther's calculator made an arguably more reasonable
> assumption than Tiger's did.  I'm not sure that I would say one is clearly
> correct though.

Disagree all you want, but mathematically, you're wrong.