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

[Alex Carver]

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.