[ale] [OT] Strange Request: Demonstrate a Calculator is Working Correctly

[Tom Freeman]

Alex - that's cool! Thank you!

On Sun, 20 Sep 2015, Alex Carver wrote:

> I'm trying to remember a division test but the first multiplication test
> that I know is:
>
> 12345679 * 9 (note there is no 8 anywhere in there).
>
> It should come back with a string of 1's.
>
> You could reverse that problem, too, type in nine 1's and divide by 9 to
> get 12345679.  If a rounding or representation error exists then it
> might show up here.
>
> On 2015-09-20 06:37, Tom Freeman wrote:
>>
>> I ran into a problem a while back, and I'm wondering if anybody has a
>> decent answer.
>>
>> Working at the board, I raced the students to get a calculation
>> performed. I shouldn't have bothered. Our respective results diverged
>> about the fourth place, with my little TI-30XA being a minority of one.
>> (Sadly, I didn't think to write the problem down for further
>> investigation.) I switched to a backup graphing calculator, and things
>> went smoothly.
>>
>> Question that some googleing hasn't properly answered: How do you test a
>> simple hand calculator to demonstrate proper operation?
>>
>> Obviously, the simple response is to dump the suspect calculator. Trash
>> it with extreme predjudice as it were.
>>
>> However, since there are individuals on this list who need extended
>> precision in their work, I wonder if they know how to test a hand
>> calculator for correctness.
>>
>> Come to think of it - having a faulty calculator or three and a testing
>> procedure might be a good instructional process for students. We do need
>> to trust our equipment, and we need to continuously check it for error.
>>
>> In any event, my thanks to the list for the use of their bandwidth.
>
> _______________________________________________
> Ale mailing list
> Ale at ale.org
> http://mail.ale.org/mailman/listinfo/ale
> See JOBS, ANNOUNCE and SCHOOLS lists at
> http://mail.ale.org/mailman/listinfo
>