Grasple has multiple check methods using the Computer Algebra System (CAS) which can be used within the editor to indicate when the answer of a student should be marked correct/incorrect. A full list of current options can be found in this article.

This article covers the Parallel to check. There are four sections in this article:

If you want to check whether the student answer is a vector and that vector is parallel to a given vector, you should use this check. A simple example would be: "vector(1, 2, 1)" is parallel to "vector(2, 4, 2)" but not to "vector(1, -2, 1)".

If you only want to check whether the vector is algebraically equal (e.g. "vector(1, 2, 1)" is equal to "vector(1, 1+1, 1)"), use the Algebraically Equivalent check.

The method uses similar logic as the Algebraically Equivalent check for vectors. In addition it also checks whether the vectors are parallel, allowing more answers to be marked as correct.

The following steps describe in short how to do this.

Build up your exercise as you always do: add a description of the question, add the question itself, provide a correct answer (in the answer box) and (optionally) add more detailed feedback.
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See an example below:

Click on the "edit answers and specific feedback" button and change the relation for the main (i.e. first) answer rule to "Parallel to".

Give a vector as the correct answer in the answer box. This vector will be used to check whether the vectors given by learners are also correct by checking whether they are parallel.
To create a vector, use the matrix form and select the dimensions of your vector.

Step 4: test different correct and incorrect answers

For our sample exercise a correct answer is the vector given by the creator or any vector which is the original vector multiplied by a non-zero scalar.
An example of a correct answer:

And an incorrect answer for our sample exercise is any vector which is not parallel to the vector given by the creator.

Automatic feedback will be shown to student about whether they have the answer correct or incorrect including a correct answer.
However more detailed explanation on when answers are correct help the learners in learning from both their correct as incorrect answers.
You can add general feedback in the green "Detailed solution" box and orange "Question at wrong answer" box. For more specific feedback based on the characteristics of the student answer, check out the answer rules options.

The method checks whether the difference between the given vector and the student answer differs by a constant value. One exception is added: if the constant is zero this is not seen as parallel. This prevents that the zero-vector answer is always seen as correct.

If the given vector to check against is a zero-vector, any vector of the same dimensions will be marked "Parallel to".

Do you want to know more about this check, whether you should use it for your exercise or any of the other checks? Please let us know via the chat icon in the right bottom of the screen!