Microsoft Excel’s New Math

We tend to trust numbers that spit out of spreadsheets, right?  I mean, computers are objective and trustworthy!

Not so much.  Excel 2007 has a major bug.  If you multiply 850 times 77.1, the answer comes out to be 100,000.

Maybe it’s time to update Pierre Gallois’ famous quote:

“If you put tomfoolery into a computer, nothing comes out of it but tomfoolery. But this tomfoolery, having passed through a very expensive machine, is somehow ennobled and no one dares criticize it.”
- Pierre Gallois

How about ..."And even if you put good numbers into Excel, tomfoolery may still come out.”

Even my old slide rule, with its 3-sig limited accuracy, delivers 65,5xx… a much smaller error, and easy enough to resolve to the full number with a couple more steps.

Updates: 

  • In the comments Ed posted a very good link below to Joel On Software Explaining the Excel Bug - especially interesting because Joel worked on early versions of Excel.
  • and Mark at Good Math, Bad Math, discusses The Excel 65,535=100,000 Bug and floating-point operations as related to display and printing.

Posted by George on 09/25/07 at 08:42 AM
Geeky • Software • Link
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