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  1. #41  
    No as i mentioned above, it depends on which inputmethod your calculator is using.

    Math is the same on every calculator :P (assuming the developer was no fool )
  2. Rob
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    #42  
    Quote Originally Posted by nhavar View Post
    It sounds like MS Calc, MetaCalc and some others dumb down math and provide some convenience methods over accuracy.

    Using paper, MS Excel, or the Pre:
    100 + 5% is the same as 100 + 0.05 which equals 100.05.

    Using MS Calc/MetaCalc:
    100 + 5% is the same as 100 + (0.05 x 100) which equals 105.

    Doing the math in your head you make the connection that 5% is 5% of 100, you internally expand the calculation to 100 + (100 x .05). However these tools are not connected to your brain. These tools make assumptions based on what you've entered. I'd never want a calculator to make assumptions about a calculation. That leads to very bad math.
    I agree, this behavior is strange (NOTE: I just tried this on my iPhone -- have to rotate to advanced landscape mode to get the % operator -- and it does the same as MetaCalc).

    The reason this is so strange?
    Try typing: 5 % --> you get 0.05
    Now type: + 5 % --> you get 0.0525 !!!!

    In other words, the behavior in the OP's example is not only different from other calculators but it is different than the behavior of the same button on the same calculator in a different situation!

    :: head explodes ::
  3. larnapp's Avatar
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       #43  
    Quote Originally Posted by Kxen View Post
    Okay. I joined to answer your question ;P

    I must say that i have no pre right now but i think i can say something about the difference of calculators.


    The calculator you linked (and the Windows Calculator too) are so called immediate execution calculators.
    That means that every time you enter something it is immediatly calculated

    A socalled infix notation calculator is wayting until you typed the whole equation and hit =

    I hope that helped

    btw if you set your Windows Calculator to scientific it is a infix calculator and not longer an immediate execution calculator.

    regards
    BRILLIANT!! This makes perfect sense! Thank you Kxen for your educated and accurate contribution.

    So now the question becomes, "Why did Palm decide the Pre should have an infix calculator rather than an immediate execution calculator?"

    While this question is more accurate it leads to fewer people posting "user error" comments or explaining basic math and is therefore more esoteric and potentially less exciting. (Sorry)
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    #44  
    Quote Originally Posted by dave75 View Post
    How else can 5% be interpreted other than .05? It's math, there's no other way to interpret it.

    EDIT: I'm not saying people are idiots either, I'm just saying that any calculator that says 100 + 5% = 105 is not a good calculator.
    I'm not saying the 'math' is different, but the OP is absolutely right:
    on Pre: 100 + 5% = 100.05
    on Windows Calc: 100 + 5% = 105

    It's the way the calculator is programmed to use the % symbol. One assumes 5% means 5/100, and the other assumes you mean 5% of the other part of the equation 100 + 5% (of 100). Excel does this too.

    It's not the math, it's the way the % is used, as others have explained much better than me before...
  5. groovy's Avatar
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    #45  
    I'm glad I slept through 3rd grade.
  6. #46  
    Normally an infix calculator is easier to use.

    if you type 2 + 3 * 2 an infix will calculate it correct and an immediate won't.
    you have to rearrange the formula to 3 * 2 + 2 and with bigger formulas that will screw you up.
  7. #47  
    Quote Originally Posted by dcdttu View Post
    I'm not saying the 'math' is different, but the OP is absolutely right:
    on Pre: 100 + 5% = 100.05
    on Windows Calc: 100 + 5% = 105

    It's the way the calculator is programmed to use the % symbol. One assumes 5% means 5/100, and the other assumes you mean 5% of the other part of the equation 100 + 5% (of 100). Excel does this too.

    It's not the math, it's the way the % is used, as others have explained much better than me before...
    Exactly but the title of the thread reads "Pre Calculator = Bad Math", which the Pre is not using "bad math."
  8. larnapp's Avatar
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       #48  
    Quote Originally Posted by jhebert121 View Post
    Exactly but the title of the thread reads "Pre Calculator = Bad Math", which the Pre is not using "bad math."
    Sorry. If I could re-title it I would pick something like,"Pre Calculator = Different Results than most other PDA and desktop calculators + a thread full of some math lessons and a few flames for good measure"
  9. #49  
    You must be a really great tipper! Or maybe you have percent confused with per-volume..... what does that mean?
  10. #50  
    Quote Originally Posted by larnapp View Post
    Sorry. If I could re-title it I would pick something like,"Pre Calculator = Different Results than most other PDA and desktop calculators + a thread full of some math lessons and a few flames for good measure"
    That about sums it up!
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    #51  
    Quote Originally Posted by larnapp View Post
    Sorry. If I could re-title it I would pick something like,"Pre Calculator = Different Results than most other PDA and desktop calculators + a thread full of some math lessons and a few flames for good measure"
    Keeps people on their toes.

    On a side note, a homebrew expression calculator would be a welcome addition.

    EDIT: If any developers are reading this, one that keeps a history/running total would be ideal .
  12. slikone27's Avatar
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    #52  
    I do see what you mean though. My Pre and my 800w calculate it different. When I tried a regular calc it came out 105 just like the 800w. On the pre it comes out as 100.05 since the Pre converts it first.
  13. #53  
    Also another way to look at it: when adding, the number can be switched around.
    Ex. 5+2=7
    2+ 5=7

    But if you reverse the original formula (100+5%) on say your PC, you get 100.

    Just different types of calculators...
  14. #54  
    Much easier to multiply by 1.05... my $0.02
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    #55  
    a fail thread like this comes along but so often...wow
  16. Clack's Avatar
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    #56  
    Readining, I feel like I am watching 5 blind philosophers all given a different part of the elephant to examine and all coming up with equally valid yet nonsense answer because you cannot see the big picture.
    "We must not contradict, but instruct him that contradicts us; for a madman is not cured by another running mad also." - Dr. An Wang
  17. #57  
    Wow... Lol waaaaay over my head
  18. #58  
    A-L-R-I-G-H-T-Y!!!!

    You want to see something funky....All of you who have calculators that give you 100+5% = 105

    Try:

    1+5% and see what it gives you!

    1.05!!!!

    At this point, I thought I knew what was going on. I assumed it was somehow assuming some new base value of the percentage based on the previous operand.


    try Test # 3!!!!

    6 + 5%

    equals 6.3!!!!

    so it's taking 6 + .05*6, 1+.05*1, 100+.05*100

    which makes sense....5%=5%=5%=5%=5/100=0.05

    The calculator is making the algebraic assumption that you mean:
    100 + (5% x 100)
    1 + (5% x 1)
    6 + (5% x 6)

    This sounds like something built for accountants and not mathematicians or engineers.
    Last edited by Nurgling; 07/30/2009 at 04:25 PM.
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    #59  
    I think the Pre is using illogical math because a percentage is not a value. It's a portion OF something. A value plus a percent does not equal a value unless the percentage is based on a specific value. Why is it assuming that you want 5 percent of 1?

    If you enter 100 + 5 %, it should throw an error that not enough information is given. If someone were to say "I want 50%", would you know what to give them? If they were to say "I want 50% of your sandwich", would you then understand what they're talking about?

    However, I can understand if calculators want to help you, as many do by assuming that the percentage relates to the previous value. So, to fill in the blank of the statement "I want 5% of ____" it's assuming you're talking about the previous value. The Pre assumes, inexplicably, that the blank is 1. Why? Who knows, but its not very helpful.
    Last edited by wicketr; 07/30/2009 at 04:33 PM.
  20. #60  
    Sorry Wicketr, but I don't believe that is correct. By definition, 5% = 5/100 = 0.05. "Percentage" is from the latin Per Centum, which means of or over 100.

    I threw these into MathCAD, and the results support my understanding (attached).

    The more I think about this, calculators are doing tihs as a convenience (i.e. fast algebra) for accounting types who want to know what a 5% rate of return is on $22,465.43 (edit: but even those calculators are still using 5%=0.05, as I showed in my previous post).
    Attached Images Attached Images
    Last edited by Nurgling; 07/30/2009 at 04:48 PM.
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