[LON-CAPA-users] Illegal division by zero

[Rex Abert]

Bob-

This might be a browser-specific phenomenon.  One popular browser is known to be non-compliant with W3C standards.  One thing that *might* help is to combine all your scripts into one script at the beginning of the problem.  The way it is written now, the variables $f1 and $ansa might not have values assigned to them in the second script, since there values were set in a different script---an issue with the scope of the variables.

It would be interesting to ask your students which browser was in use when the error occurred.

Rex Abert
Associate Professor of Mathematics
Tallahassee Community College
________________________________________
From: lon-capa-users-bounces at mail.lon-capa.org [lon-capa-users-bounces at mail.lon-capa.org] on behalf of Bob Gonzales [rgonzal at binghamton.edu]
Sent: Friday, May 29, 2015 12:21 PM
To: Discussion list for LON-CAPA users
Subject: Re: [LON-CAPA-users] Illegal division by zero

Rex,

Here's the code, I thought it might be easier to cut and paste it in construction space to make it easier to debug.  The problem works fine for me in construction space.   One student with $f1=1.0 and one student with $f1=6.0221e23 have gotten it correct so far.

<problem>
<part id="t06p12a">
<script type="loncapa/perl">
$n1=&random(0.025,0.050,0.001);
$t1=&random(1,2);
$unit1=&choose($t1,"moles","molecules");
$f1=&choose($t1,1.00,6.0221e23);
$mw1=(12.011*20.0)+(1.008*24.0)+(15.999*2.0);
$ansa= $n1 * 1e-3 * $f1/ $mw1;
</script>

<startouttext />
<p>A particular oral contraceptive contains &format($n1,'3f') mg of ethinyl estradiol
in each pill. The formula of this compound is <chem>C20H24O2</chem>.
How many $unit1 of ethinyl estradiol are there in one pill?  (give answer to 3 digits)</p>
<endouttext />
<numericalresponse format="3e" answer="$ansa" id="11">
<responseparam name="tol" type="tolerance" default="5%" description="Numerical Tolerance" />
<responseparam name="sig" type="int_range,0-16" default="3,4" description="Significant Figures" />
<textline />
<hintgroup>
<startouttext /><endouttext />
</hintgroup>
</numericalresponse>
</part>
<part id="t06p12b">
<script type="loncapa/perl">
$t2=&random(1,3);
$sub2=&choose($t2,"carbon","hydrogen","oxygen");
$f2=&choose($t2,20.0,24.0,2.0);
$ansb=($ansa/$f1)* $f2 * 6.0221e23;
</script>

<startouttext />
<p>How many $sub2 atoms are there in one of these pills (due to the presence
of ethinyl estradiol)?  (give answer to 3 digits)</p>

<endouttext />
<numericalresponse format="3e" answer="$ansb" id="12">
<responseparam name="tol" type="tolerance" default="5%" description="Numerical Tolerance" />
<responseparam name="sig" type="int_range,0-16" default="3,4" description="Significant Figures" />
<textline />
<hintgroup>
<startouttext /><endouttext />
</hintgroup>
</numericalresponse>
</part>

<part id="t06p12c">
<script type="loncapa/perl">
$mw3=&choose($t2,12.011,1.008,15.999);
$ansc=$ansb*$mw3/6.0221e23;
</script>

<startouttext />
<p>What mass of $sub2 is this? (Enter the answer in grams.)</p>

<endouttext />
<numericalresponse format="3e" answer="$ansc" id="13">
<responseparam name="tol" type="tolerance" default="5%" description="Numerical Tolerance" />
<responseparam name="sig" type="int_range,0-16" default="3,4" description="Significant Figures" />
<textline />
<hintgroup>
<startouttext /><endouttext />
</hintgroup>
</numericalresponse>
</part>
</problem>