MathGroup Archive 2001

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repeating decimals

  • To: mathgroup at
  • Subject: [mg29200] repeating decimals
  • From: Tom De Vries <tdevries at>
  • Date: Sat, 2 Jun 2001 17:56:09 -0400 (EDT)
  • Sender: owner-wri-mathgroup at


I am working on a simple notebook to illustrate repeating and terminating
decimals for a junior high math class.

I know the topic  of representing decimal numbers has been discussed here
before, but I am still a bit confused....

On my Mac


"4.0 for Power Macintosh (July 20, 1999)"

Why does

N[1/2, 10]

give me


and why does

N[1/2, 20]

give me


why does

NumberForm[7/13. , 15,   DigitBlock -> 6, NumberSeparator -> " "]

give me 

0.538461  538461  539

and why does

NumberForm[7/13. , 30,  DigitBlock -> 6, NumberSeparator -> "  "]

0.538461   538461    5385

It seems to me that the number of digits I am asking for is not related to
what I actually get.  Is there a way to ask Mathematica to represent the
decimal approximation that would be consistent?

Thanks for any help you might provide


Tom De Vries

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