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.

1. When to use the numerical check?

2. Example cases

3. How does the numerical checks work?

## When to use the numerical check?

If you want to check whether a student answer (evaluates to) a numeric value, you should use this check. For example, the answer "1" is numeric, while "x" is not.

You can apply this method to:

• exact numbers or expressions (e.g. 3, pi or 4 + 5)

• vectors and matrices

• unordered collections/lists

• sets

• intervals

In case of a collection of numbers in the form of lists, sets, matrices or intervals this method returns 'True' if all elements in the collection are numerical, and 'False' if any element is not.

## Example cases

The list below shows some examples: There are two important observations that can be made based on these examples:

1. The method evaluates whether the result of a given expression is a number. Because of this, the expression 'x divided by x' is considered to be numerical.

2. Infinity itself is not a number, but can be used in an open interval. In this case Infinity is not considered to be part of the set.

## How does the 'Numerical' checks work?

If the input is a single expression the CAS checks if the result of the simplified expression is a number. In the case of a collection, the CAS first transforms all elements of the collection to a list of expressions and checks if all expressions evaluate to a number. Simplification is done using the mathematical rules within CAS.

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!