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  1. Silver5's Avatar
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       #1  
    I entered the following:

    10 + 8% =

    ...and the answer I get is 0.18

    Well, when I enter the exact same thing on my Treo 600 I get 10.8 as the answer...seems better, right? So I tried the calculator on my iPAQ and got 10.8 as well. the I pulled out the TI-83 from a few years ago in statistics. I got 10.8. Oddly enough, even when I do it by hand, I get 10.8.

    So why can't the Treo 650 do this correctly?

    It gets worse. I switched to the advanced mode and did the calculation on the 650 and got 10.64.

    So, I suggest that those of you who use your calculators look into something other than what comes bundled, because I sure as hell wouldn't trust it.
  2. #2  
    Not a mathmatician - but I think it has to do with the fact your question doesn't have enough data. 8% of what? The 650 assumes you mean 10% + 8% and thus gives you 18%
  3. #3  
    LOL well I tried it on my Sony Clie NX-80 and a few other calcs I have laying around. Your right. The 650 gives a different result then the rest. Wierd

    Should note. It does give the correct result if you enter a percent as a decimal and avoid using the percentage key.
  4. Silver5's Avatar
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       #4  
    Ok, sorry...

    I simplified the numbers from those that I initially used, and recalculated using the small numbers 10 and 8% (of ten).

    If I want to find out what the sales tax is that I should be paying on an item I type into the Treo 650 the following:

    10 + 8% =

    This stands for ten dollars, plus 8 percent of ten dollars. I then hit the "equals" key to tell it to calculate. This works properly on every other calculator I have tried, but not on the 650's calculator.

    The item I was actually doing this for actually cost me $429. With sales tax at 8% it cost $463.32. Correct me if you think I'm wrong. The Treo 650 is coming up with $4.37. No typo there either. Either this calculator requires a different way to input this information, or it is not accurate.
  5. #5  
    I see what your doing - as I am unfamiliar with the language Treo uses hard to say.

    Why not just to "10 x .08" and that will give you the tax.

    Either way - it is kinda odd that they give different interpretations.
  6. #6  
    I think I agree with both posters here. The key sequence "10 + 8 %" is ambiguous and open to interpretation. However, the standard interpretation (at least on the 4 non-RPN calculators I could find in my house) seems to be 10 + (.08 * 10)
  7. #7  
    It seems clear that what it actually did is first add 10 and 8 and then divide by 100 (the "%" key), which makes perfect sense for this calculator.

    Try this:

    10 + 8 X. 01. The result is .18, though of course it really should be 10.08 if normal math rules of precedence were applied, doing the multiplication first, then the addition.

    Note that if you do the same thing in "advanced" mode you get 10.08 as the result!

    Obviously, in "basic" mode the operations are all done as you go, while in "advanced" mode normal rules of math apply.
  8. #8  
    So is this something we can add to the Treo 650's already long list of "shortcomings"?
  9. #9  
    Quote Originally Posted by IsLNdbOi
    So is this something we can add to the Treo 650's already long list of "shortcomings"?
    Nope. This is not a shortcoming. This is more like "operator error." 10 + 8% is an incorrect way to figure out 8% tax. Try 10 X 1.08. Simple, eh?

    Frannkly, no calculator should have a "%" key as its operation is confusing and the way it works is not universal.
  10. #10  
    Quote Originally Posted by westronic
    Nope. This is not a shortcoming. This is more like "operator error." 10 + 8% is an incorrect way to figure out 8% tax. Try 10 X 1.08. Simple, eh?

    Frannkly, no calculator should have a "%" key as its operation is confusing and the way it works is not universal.

    I'm talking about what the original poster said:

    10 + 8% =

    ...and the answer I get is 0.18


    I use the % button alot and if the Treo650 doesn't give the correct answer when you use x + y%, then it's not working correctly, thus another "shortcoming".
  11. #11  
    You can't really say it gives the wrong answer when the function of the key is not documented. It obviously is not the answer you expected, and it may not be the same as other implementations, but as has been pointed out, it is a valid answer given strict left-to-right operation hierarchy.
    Palm Pilot Personal -> Palm III -> Palm IIIx -> Visor Prism -> Clie TJ37 -> Treo 650 -> GSM Centro
  12. #12  
    Quote Originally Posted by IsLNdbOi
    I'm talking about what the original poster said:

    10 + 8% =

    ...and the answer I get is 0.18


    I use the % button a lot and if the Treo650 doesn't give the correct answer when you use x + y%, then it's not working correctly, thus another "shortcoming".
    No, as I said, different calculators work different ways. On some calculators, 10 + 8 x .01 would be 10.08 and on others .18. The "%" key is a particular problem in this area if it is not used correctly - as in "10 + 8 %" and expecting 10.08 - sometimes you'll get that, sometimes you won't, depending upon the calculator involved.

    A basic calculator, as the one being discussed here, usually processes each operation as you go, thus 10 + 8 % would be .18 because the "10 + 8" is processed first. More advanced calulators, as even this one in "advanced" mode, process operations using normal precendence of multiplication over addition, so, for 10 + 8 %, the "%" operation is processed before the addition - though the "%" operator is missing in the advanced calculator and you actually have to know how to do this using 10 x 1.08 to get the right answer.

    That's the way it is and it is NOT an error or shortcoming, it's a lack of understanding in how calculators work.

    It's worth noting that on calculators that give you 10.08, they would also give you 11.08 if you did 11 + 8%, which would NOT be what you want if you are trying to get to 11 + 8 percent of 11. In this case, the use of the "%" key is incorrect.

    The CORRECT way to do this problem is 10 x 8 % + 10. This gives you 10.08 on ANY calculator. 10 +8% is simply the wrong way to enter this problem, as I showed with the example of using "11" instead of "10."

    The fact that "10 + 8 %" gives you 10.08 on some calculators is purely fortuitous because you happened to choose "10" as your base number - other numbers give "incorrect" answers. The answers are all correct, of course, once you understand how the calulator is working.
    Last edited by westronic; 03/12/2005 at 09:43 AM.
  13. #13  
    bravo westronic.
  14. #14  
    wouldn't you want to do, 10 * 1.08, ie: 10 * 108%
  15. #15  
    I am not a math wiz but sschwar's example is how I do it to get total price
  16. #16  
    Quote Originally Posted by Celestial
    I am not a math wiz but sschwar's example is how I do it to get total price
    Assuming what you want is to add 8% tax to a total of, say, $23, the correct way to enter this on ANY calculator with a "%" key is:

    23 X 108 %

    Just as sschwar2 showed us.

    That is the same thing as 23 X 1.08 (which is really the better way to do this calculation - no possible ambiguity over the use of the "%" key) which gives you the correct result - the same as 23 + (8 percent of 23).

    I intentionally picked "23" because there is no way to use the "%" key incorrectly to get the correct result, as there is with "10."
  17. #17  
    OK OK stop it! There is no damned debate here guys! Any other standard calculator on the planet worth it's salt will give you this: 10 + 8% = 10.8 (or 10.80 depending on where you have the decimal set).

    The calculator is screwed... just deal with it.
  18. #18  
    FWIW, if you wanted to add 8% to some number, the math would NOT be 10 + 8 x .01 as suggested by westronic. It would either be 10 + 8 * 0.1 OR 10 + 80 * 0.01. As long as we trying to be accurate. Also, FWIW, in basic mode, if you just want to know what the amount of the percentage is, i.e. what is 8% of $429, instead of hitting 429 + 8%, if you hit 429 * 8% you will get the result you want. Either that, you can do what most of us do, as suggested above, and multiply the item cost by 1.08. That'll work everytime on every calculator.
  19. #19  
    Quote Originally Posted by creighton
    FWIW, if you wanted to add 8% to some number, the math would NOT be 10 + 8 x .01 as suggested by westronic...
    Please re-read my post - you'll find that's NOT what I suggested.
  20. #20  
    Quote Originally Posted by westronic
    Please re-read my post - you'll find that's NOT what I suggested.
    Gosh Westy, I can't believe you don't know how to perform such a simple calculation. . .
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