## WeBWorK Problems

### Fractions-NoDecimals for Matrices

by Brittni Lorton -
Number of replies: 1

I have having a strange issue pop up in the below problem. I want to ensure students only enter fractions, and not decimals. The code here seems to be working, but when a student enters the decimal value for the [1,1] entry and the fraction value for the other entries, they just get 'incorrect' and not the message saying they need to use fractions. When a student enters the decimal in the [2,2] entry they get the desired message of 'in entry (2,2): You are only allowed to enter fractions, not decimals." Weird! Any insight as to why this is and if there is a fix?

DOCUMENT();

"PGstandard.pl",

"MathObjects.pl",

"PGchoicemacros.pl",

"PGmatrixmacros.pl",

"parserAssignment.pl",

"PGML.pl",

"MatrixReduce.pl",

"PGcourse.pl",

);

TEXT(beginproblem());

##########################

#  Setup

Context('Fraction-NoDecimals');

Context()->parens->set("[" => {formMatrix => 1});

do {

$a = random(-1,1,2) * random(2,9,1);$d = random(-1,1,2) * random(2,9,1);

$b = 0;$c = 0;

} until ($a !=$d);

$A = Matrix([[$a, $b], [$c, $d]]);$A = apply_fraction_to_matrix_entries($A);$Ainv = $A->inverse;$Ainv = apply_fraction_to_matrix_entries($Ainv); Context()->texStrings; BEGIN_TEXT If $$A = A,$$$BR

then

$BR $$A^{-1} =$$ \{$Ainv->ans_array(7) \}.

$BR Enter elements as fractions, not decimals. END_TEXT Context()->normalStrings; ANS($Ainv->cmp);

COMMENT();

ENDDOCUMENT();