** Using WeBWorK **

Holly

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Can you give us some more informationn on this? E.g. what problem is the student working on? Entering 1/12 (when I try it) gives the correct response and entering 1/12+, 112, 12+ all give syntax errors as they should.

Are other students having similar problems?

Arnie

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Holly

##DESCRIPTION ## Evalute a limit of a fraction of two polynomials, ## involves factoring ##ENDDESCRIPTION

##KEYWORDS('limits', 'factoring')

DOCUMENT(); # This should be the first executable line in the problem.

loadMacros( PG.pl, PGbasicmacros.pl, PGchoicemacros.pl, PGanswermacros.pl, PGauxiliaryFunctions.pl );

TEXT(&beginproblem); $showPartialCorrectAnswers = 1;

@rt = (4,9,16,25,36); $i1 = random(0,4,1); $c = random(1,10,1); $a = $rt[$i1]; $b = $a+$c; $a2 = $a**.5;

TEXT(EV2(<<EOT)); Evaluate the limit [ lim_{ x rightarrow $b } frac {sqrt{x-$c}-$a2 }{x-$b} ] $BR {ans_rule(10) } $BR EOT

$ans = 1/(2*$a2); &ANS(num_cmp($ans));

ENDDOCUMENT(); # This should be the last executable line in the problem.

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This problem just uses the standard answer evaluator num_cmp which has been used by many thousands of students.

Could it be that the student entered 1/12 0 (1 slash 12 space 0)? WeBWorK interprets a space as multiplication (jutaposition) and this gives 0. At least that is what WeBWorK is telling you that the student entered. Did you see what the student entered? Can this bug be repeated?

Arnie

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Ways of testing for this are to look at the answer logs, or the database for the last answer, or to click in the answer blank and hit delete/backspace a lot, or to enter the problem and don't have webwork enter the previous answer for you.

On webwork's side, I think one of the bits of tidying it should do to student answers is to replace all sequences of whitespace with a single space. That should keep answers readable, but eliminate the problem I described (which may or may not be Holly's problem).

John

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