Hi Gene,
most likely the problem is one of number representation (which
contributes to rounding errors).
The binary representation of $Av+0.05 is (by which I mean "the result of
binary representation of $Av plus binary respresentation of 0.05 as a
binary")
10.101100110011001100110011001100110011001100110011001
whereas the binary representation of 2.7 is
10.101100110011001100110011001100110011001100110011010
Both binary numbers differ only in the last two digits and the second
one is larger. That explains why 2.7 is not accepted.
I have done the computations on 64-bit machine which likely matches
your server's resolution.
I hope this is of help.
Peter
Am 22.09.2019 um 02:51 schrieb Harding, Gene L:
Hi everyone,
I have a quiz problem in LC that seems to be doing some odd things
with the rounding. I have successfully recreated the problem reported
by one of my students, but cannot figure out why it happens.
The answer to the problem (part c) is 2.65 on the dot. The problem
requests an answer with one place after the decimal, and the tolerance
is +/- 0.05. In this case, since the value computes to exactly 2.65,
LC should take anything from 2.6 to 2.7. In fact, in author view LC
indicates it will take anything from 2.6 to 2.7:
The trouble is that 2.6 works, 2.65 works, but 2.7 does not.
This is the Perl script calculation (Rf=33, Ri=20):
$Av = 1+$Rf/$Ri; # Gain
This is the response code:
<numericalresponse unit="" format="1f" answer="$Av" id="3">
<responseparam name="tol" type="tolerance" default="0.05"
description="Numerical Tolerance" />
<textline readonly="no" spellcheck="none" />
</numericalresponse>
Any idea what the problem is? I am baffled.
Best regards,
Gene L. Harding, PE
Associate Professor of ECET
Purdue University
574-520-4190
https://polytechnic.purdue.edu/south-bend/
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Peter Riegler
Fakultät Informatik
Ostfalia Hochschule für angewandte Wissenschaften
- Hochschule Braunschweig/Wolfenbüttel
Salzdahlumer Str. 46/48
38302 Wolfenbüttel
Tel 05331 939 31540
Fax 05331 939 31542
Web www.ostfalia.de/pws/riegler
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