** Using WeBWorK **

Collect like terms: 3x+2x

From what I see, the 'standard' way of asking this question in Webwork would be to ask about the value of a coefficient of x. Unfortunately, with our population of students, that would not be good enough (common answer among our students would be 5x^2, so asking just about a coefficient would not address this problem). I am guessing, that asking students an open question (i.e. expect them to give the answer 5x), would cause the following problem: If a student enters as an answer 3x+2x (in other words, do nothing, merely rewrites the problem), the correct answer would be granted to him. Am I right?

What one can do to guard against answers like that is to, in addition to comparing student's answer to correct answer, read student's answer as a string of symbols and, for example, in this case, make sure that there is no '+' symbol or (after removing blanks), count number of symbols in a string and make sure it is not too long (or something of this kind). Would that type of coding be possible (I believe I saw some examples, where similar things were done)? Or maybe there are more straightforward ways of handling this type of questions? Can one use some logical functions in the process of evaluation of an answer (correct if a=true and b=true?). Would the answer 3x+2x, when read as a string be still '3x+2x'?

I am asking because, before Webwork, I 'experimented' a little bit with Maple TA (I am sure, you know it is a commercial competitor of Webworks) and I had the following problem: Maple automatically was converting 3x+2x to 5x and even when I was trying to read student's answer as a string, I was not able to distinguish between 3x+2x and 5x (I eventually succeeded). Would that be a case with Webwork?

YOUR HELP WITH ANSWERING MY QUESTION WOULD BE GREATLY APPRECIATED. I AM TRULY EXCITED TO TRY TO USE WEBWORKS FOR OUR STUDENTS, BUT THE TRUTH IS, I AM AT THE 'POINT ZERO' (I WILL HAVE TO LEARN EVERYTHING FROM SCRATCH TO START USING IT), SO IF I KNOW IN ADVANCE, THAT THE ABOVE 'A MUST' QUESTION CANNOT BE HANDLED BY WOBWORK, I SHOULD NOT EVEN START.

I look forward to hearing from you. Thank you very much for your time.

Regards,

Margaret Wojcicka

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I can answer some of your specific questions (e.g. if you require the student to enter "5x" as a string, then "2x+3X" would not be accepted. It would be easy to also accept something of the form " 5x " or even " 5 x " if you wanted) but at Rochester we do not have any experience writing the kinds of questions you are interested in. What would be really useful would be for someone who has this experience with these types of questions to respond. E.g. someone using WeBWorK in a remedial college math course or in a high school course. If necessary, we can provide you with names of some people that have more experience with these types of courses than we do, but first I'll take the liberty of posting your question and my response on our discussion group http://webhost.math.rochester.edu/webworkdocs/discuss/ and se if anyone responds.

Arnie

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Davide added this a while back. Here is an untested sample:

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

loadMacros(
PG.pl,
PGbasicmacros.pl,
PGanswermacros.pl,
"contextLimitedPolynomial.pl"
);

Context("LimitedPolynomial")->flags->set(singlePowers=>1);

$a = random(2, 4);
$b = $a+random(1, 3);

TEXT(beginproblem());

BEGIN_TEXT
Simplify: \( $a x + $b x =\)
\{ ans_rule(20) \}
END_TEXT

$c = $a+$b;
ANS(Formula("$c x")->cmp);

ENDDOCUMENT();

John

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