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MathGroup Archive 2005

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Re: Adding two numbers of high precision results in a number of low precision??

  • To: mathgroup at smc.vnet.net
  • Subject: [mg56960] Re: Adding two numbers of high precision results in a number of low precision??
  • From: Paul Abbott <paul at physics.uwa.edu.au>
  • Date: Wed, 11 May 2005 05:24:23 -0400 (EDT)
  • Organization: The University of Western Australia
  • References: <d5mv2v$dv0$1@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

In article <d5mv2v$dv0$1 at smc.vnet.net>,
 Kees van Schaik <schaik at math.uni-frankfurt.de> wrote:

> how is it possible that if I add two numbers of precision ca. 390 I get 
> something of precision 53 back? 

It is quite easy. For example, try this

  a = 1`390

  b = -1`390 + 10^(-335)

  Precision[a]

  Precision[b]
  
  Precision[a + b]

Cheers,
Paul

-- 
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