When a student responds to a numeric question with a fraction using the backslash key / (eg, 3/10), Canvas removes the backslash (eg, 310) when the student submits. Fraction answers aren't supported for numeric questions in standard Quizzes either (only for Essay question types), but students will see that the backslash was removed before submitting the quiz.
In Quizzes.Next, students don't know that the backslash isn't supported and can submit an answer that displays as a fraction until after the quiz is submitted and they see their responses.
I submitted a ticket for this issue since it seems to be a bug with Quizzes.Next, but wanted to bring it up here, too, in case anyone else comes across it.
Update: As of 2/8/19, Canvas will give students the following warning message if they try to submit a quiz and have included special characters in a numerical question answer:
This does not affect answers containing a "-" to signify a negative number.
I'm also having the same problem as well, except that it does take the backslash into consideration:
Fractions marked incorrect in numerical answer questions
In the picture above, 2500/3 = 833.33. Can you please help what's going on?
firstname.lastname@example.org You've just hit on a recent and significant pain point regarding numeric questions in New Quizzes.
In the example you shared, the student's answer is marked incorrect because Canvas is looking for an exact match to 833.33. What you should be able to do is to add the fraction "2500/3" as another possible answer and regrade the question to accept both 833.33 and 2500/3 as correct answers. However, while students can enter fractions and other non-numeric values (eg, $, %, abcde . . ) as answers for numeric questions, teachers cannot. The change to accept any type of values in a student's response to a numeric question occurred sometime around February 2019 and was NOT communicated to end-users. This is a big issue because students can answer with the correct numeric value, but if they include any additional text, their responses will be marked incorrect.
Below is an example of a student's response that was marked wrong because they included a dollar sign:
Unlike the legacy Quizzes tool, students are not prevented from inputting non-numeric values or given a warning message if they include non-numeric values. In short, students can enter any possible response for a numeric question and have no way of knowing that their response will be marked incorrect.
I created a feature idea that you can vote up (https://community.canvaslms.com/ideas/14905-new-quizzes-allow-only-numeric-values-for-numeric-questi...), but the best thing you can do is to contact your CSM and let them know how this problem is affecting you.