iPhone Calculator Error

Post by **Marvin** » Fri Oct 02, 2015 6:11 pm

Try this ... first on your computer calculator (or most any calculator) and then on your iPhone calculator:

1. Clear all (C or AC).

2. Enter the number 80.

3. Without pressing the Enter or Equals (=) button, subtract 1.

4. Again without pressing (=), divide by 2.

5. Now press the Enter or Equals button.

Check the result. Compare what you get with the computer to what you get with the iPhone.

CS-ACI- · Post by **CS-ACI-** » Fri Oct 02, 2015 10:30 pm

Hello,

Well, two different phone calculators ( Galaxy phone ) 79.5
PC calculator 39.5
PC spread sheet using "+80-1/2" 79.5

https://www.google.co.uk/?gfe_rd=cr&ei=Me35VYLVN4H98we5ioc4&gws_rd=ssl#q=online+calculator

Steve

PaulB · Post by **PaulB** » Sat Oct 03, 2015 12:55 am

I can't speak for the iphone but for Windows Calc:
try your test with Calc
then, click View - Scientifc and try it again.
Scientifc treat it as if you entered
80- (1/2) = 79.5
where as Standard treats it like
(80-1)/2

Whether that's operation as intended or a bug in Standard mode I don't know for sure but I suspect that Standard mode may be designed to to the calculation in sequential order rather than doing */ before +- calculations.
I was always a poor math student but if I recall connrectly */ normally has precident over +- unless specifically specified by using () - but I may be wrong

and based on my grades I probably am. That's why I always hated calculus.
But when I use a calc like that I generally use () when using multiple operators.

Post by **Marvin** » Sat Oct 03, 2015 1:47 am

Turning the iPhone sideways will give you the parentheses but, in the vertical, it supposes to work like any two-dollar calculator. I doubt that many people do their taxes on a scientific calculator. Instead, they probably use the same kind my wife uses for calculating her test scores.

Anyway, it certainly messed up the trig figures I was working on for an Evochron quest scenario.

Nigel_Strange · Post by **Nigel_Strange** » Sat Oct 03, 2015 1:56 am

Well, or the order of operations has you do multiplication/division before addition/subtraction, right? It's been a long time since I have taken algebra, but I think that's how it worked.

PaulB · Post by **PaulB** » Sat Oct 03, 2015 3:01 am

From post: 180991, Topic: tid=12113, author=Marvin wrote:Turning the iPhone sideways will give you the parentheses but, in the vertical, it supposes to work like any two-dollar calculator. I doubt that many people do their taxes on a scientific calculator. Instead, they probably use the same kind my wife uses for calculating her test scores.

Anyway, it certainly messed up the trig figures I was working on for an Evochron quest scenario.

If you switch to Scientific mode I didn't have to use the () to get the 79.5 results - it assumed the ().
All I did in both modes was 80-1/2=

But I'm not say you should ignore using () even in the Scientific mode - it may depend on just what you are trying to calculate as to whether you need to use them explicitly or not.
Better safe than sorry.

CS-ACI- · Post by **CS-ACI-** » Thu Oct 08, 2015 4:07 am

Hello,

B.O.D.M.A.S.

Brackets Of Division Multiplication Addition Subtraction.

But on a side note, I always use brackets even when not needed, this way I control what happens and in what order.

Steve

Post by **DaveK** » Thu Oct 08, 2015 10:45 am

I've taught this sort of stuff fairly recently and Paul and Nigel are correct. In stacked calculations (where you enter all the parts and press = at the end) all calculators should give the same answer - even if it's not the answer you thought you were asking for:D

I always suggested to my students that in longer calculations they used brackets to make it clear (to themselves as well as the calculator) the order that they wanted the calculations doing. I also suggested that they did a very rough and ready mental calculation to give a quick check that the answer on the calculator was in the ballpark at least

Post by **Marvin** » Thu Oct 08, 2015 3:12 pm

The point: I have yet to see a cheap calculator (starting in 1972) with brackets or parenthesis. I still have a number of cheap calculators and I use them all the time for balancing my checkbook and figuring speeds and times and distances in Starwraith games. Even the iPhone calculator doesn't have brackets when held in the vertical position (which, by the number of vertically oriented videos I've seen on TV and YouTube, can only mean lots of people don't even realize that they can turn their iPhones in the horizontal). But, of all the calculators I've ever used (never to do complicated math problems ... for those I run a program in DOS or BASIC or some other language), the iPhone is the only one to ... oh, what's the use.

Post by **DaveK** » Thu Oct 08, 2015 4:52 pm

I blame it all on the teachers not doing their job of teaching students how to use inadequate calculators to do calculations that are beyond the understanding of the students and the calculators themselves.

Edit: . . . or I blame it on the politicians for not getting rid of the teachers who are not doing their job of . . . etc

Edit 2: . . . or I blame it on the adults who were students who lacked the understanding but voted in the politicians who didn't get rid of the teachers who were not doing their jobs of . . . etc etc

[Edited on 8-10-2015 by DaveK]

Post by **Marvin** » Thu Oct 08, 2015 5:25 pm

When I was in school, we were taught how to use a slide rule.

Post by **Marvin** » Thu Oct 08, 2015 5:35 pm

Btw, my first calculator looked like this:

Only mine was plastic.