Re: A simple error

• To: mathgroup at smc.vnet.net
• Subject: [mg102173] Re: [mg102140] A simple error
• From: Bob Hanlon <hanlonr at cox.net>
• Date: Fri, 31 Jul 2009 05:56:59 -0400 (EDT)

```If you want exact results you need to use exact numbers rather than machine precision numbers. Use Rationalize

TEP12 = 0.11 (80000 - 12000 P + 800000 (1 - R)) +
0.11 (40000 - 12000 P + 1000000 (1 - R)) +
0.28 (-12000 P + 1200000 (1 - R));
MTEP12 = 0.11 (-130000 + 12000 (-35 + P) + 800000 R) +
0.11 (-130000 + 12000 (-35 + P) + 1000000 R) +
0.28 (-130000 + 12000 (-35 + P) + 1200000 R);

Total[Rationalize[{TEP12, MTEP12}, 0]] // Simplify

272200

Alternatively, use Chop

TEP12 + MTEP12 // Simplify // Chop

272200.

Bob Hanlon

---- Youness Eaidgah <y.eaidgah at gmail.com> wrote:

=============
Dear all,
I have faced a awkward situation in Mathematica. I want to sum the following
simple equations:

DTEP12 = 0.11 (80000 - 12000 P + 800000 (1 - R)) +   0.11 (40000 - 12000 P +
1000000 (1 - R)) + 0.28 (-12000 P + 1200000 (1 - R))
MTEP12 = 0.11 (-130000 + 12000 (-35 + P) + 800000 R) + 0.11 (-130000 + 12000
(-35 + P) + 1000000 R) + 0.28 (-130000 + 12000 (-35 + P) + 1200000 R)

Obviously, the result of the DTEP12+MTEP12 is : 272200

However, when I use the following commands

Simplify[DTEP12+ MTEP12]   or FullSimplify[DTEP12+MTEP12]

Mathematica returns: 272200.+ 0. P + 5.82077*10^-11 R. I am suprised where
the last term comes form (5.82077*10^-11 R)! It is a really really small
value, however, it is still an error. it creates some inconveniences later
in my calculations. I would appreciate if you could help me out.
Thank you,
Youness

```

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