Index: questiontype.php
===================================================================
RCS file: /cvsroot/moodle/moodle/question/type/match/questiontype.php,v
retrieving revision 1.63
diff -u -r1.63 questiontype.php
--- questiontype.php	21 Sep 2010 08:20:48 -0000	1.63
+++ questiontype.php	26 Sep 2010 16:39:46 -0000
@@ -480,7 +480,15 @@
      * calculate.
      */
     function get_random_guess_score($question) {
-        return 1 / count($question->options->subquestions);
+        $answers = array();
+        // Prepare a list of answers, removing duplicates.
+        foreach ($question->options->subquestions as $subquestion) {
+            $answertext = strip_tags(format_string($subquestion->answertext, false));
+            if (!in_array($answertext, $answers)) {
+                array_push($answers, $answertext);
+            }
+        }
+        return pow(1 / count($answers), count($question->options->subquestions));
     }
 
 /// RESTORE FUNCTIONS /////////////////