Pi wrong?


So, I've been sitting here on hold with BofA for what must seem like hours, and I'm gazing at my HP calculator poster, looking at the various models. Very pretty. ;-)

As I glance at the HP-10bii model ("R2D2"), I see the value of Pi in the display. 3.1415926545.

Wait. 545? I always knew it as 3.1415926535.

My HP-97 says 3.141592654 (using DISP), so, okay, it rounded up.

My HP-30b says 3.14159265359 (gotta love the extra digit).

I don't have an HP-10bii handy, but that value in the display, on the poster, appears to be wrong. Was it just typed in or actually displayed wrong on that unit?

Inquiring (bored) minds want to know.



The 10bii doens't have a pi key nor trig functions nor other obvious way to calculate pi so it almost certainly was typed in wrong.



IIRC pi=22/7

so any calculator ought to be able to display pi


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Sufficient for most order-of-magnitude guessing - even 3.0 would do d;-)


Not true...Pi is an irrational number.

Not much of a sense for humor or sarcasm, eh?


22/7 is off by about +4.0E-4.
245/78 is off by about -1.8E-4 (not a whole lot better).
355/113 is off by about +8.5E-8.
65298/20785 is off by about -5.1E-8.
93343/29712 is off by about -9.9E-9.
For 16-bit scaled-integer work with 32-bit intermediate results, 355/113 is usually used as it is quite accurate and you have to go to much higher numbers, all the way to 62298/20785, to get any better, and even that doesn't bring much improvement.

Edited: 30 Mar 2010, 5:50 p.m.


That's pi for the statisticians who only ever need to be 95% correct. ;)


95% are 2 significant digits only ;) Please see my post above.


My Sharp EL-5001 shows Pi as 3.141592653.

Here with a Sharp EL-515 showing Pi as 3.141592654:

Btw the EL-5001 is a pretty strange beast with mechanical/preprogrammed soft keys ~10 years before the HP-18C/28C.

Edited: 30 Mar 2010, 6:12 p.m.


Did anyone stop to think how nutty it is for grown men (woman) to be bantering back and forth for hours on such a subject?

Pi are round. Cornbread are square.


We might think of that, but put it out of our mind.

This is one of those special places where we get to eat our pi and our square roots too.


This reminds me of Donald walking through the forest of square roots in Donald In Mathmagic Land. Priceless!!


a real bad slice of pi=

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