Re: Errors with decimal addition in Mathematica 5.0

• To: mathgroup at smc.vnet.net
• Subject: [mg47427] Re: [mg47416] Errors with decimal addition in Mathematica 5.0
• From: Murray Eisenberg <murray at math.umass.edu>
• Date: Sun, 11 Apr 2004 04:44:04 -0400 (EDT)
• Organization: Mathematics & Statistics, Univ. of Mass./Amherst
• References: <200404100601.CAA24300@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

```You're confusing what you see with the numeric value actually found by
Mathematica.

If you are using floating-point numbers, then by default, Mathematica
displays only 6 digits (on most or all platforms).  To see more, use
NumberForm.

In you case:

13505.5 - 244.91
13260.6

NumberForm[%, 10]    (* look at 10 correct digits, say *)
13260.59

The value calculated by Mathematica is correct, as you can demonstrate,
for example, by something like the following:

FractionalPart[13505.5 - 244.91]
0.59

In the last output you see both correct decimal places since there's no
problem fitting all the digits into a default 6 displayed.

Peng Yu wrote:
> In[1]:= 13505.5 - 244.91
> Out[1]= 13260.6
>
> However,13505.5 - 244.91 = 13260.59. "N" doesn't help, either.
>
> In[25]:= N[13505.50 - 244.91]
> Out[25]= 13260.6
>
> But the following command gives the correct answer.
> In[26]:= 505.50 - 244.91
> Out[26]= 260.59
>
> How can I get the correct last digit? Thanks!
>
>

--
Murray Eisenberg                     murray at math.umass.edu
Mathematics & Statistics Dept.
Lederle Graduate Research Tower      phone 413 549-1020 (H)
University of Massachusetts                413 545-2859 (W)
710 North Pleasant Street            fax   413 545-1801
Amherst, MA 01003-9305

```

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