# Formulas question type

Note: You are currently viewing documentation for Moodle 2.8. Up-to-date documentation for the latest stable version of Moodle may be available here: Formulas question type.

## Usage

You would enter your 'sets' (called 'lists' in formulas questions) in the 'Random variables' field when creating question as:

```a = {100, 125, 150, 175, 200};
b = {1, 2, 3, 4, 5};
c = {10, 12, 14, 16, 18};
```

When an attempt is started a, b, and c will take a value drawn from the corresponding list at random.

You can then define other variables depending of these ones in the 'Global variables' field if you want. For instance if you need the value of a+2*b somewhere in your question text or Combined or general feedback, just define

```d=a+2*b; in 'Global variables'
```

Once you have defined your variables, you can use them in all the question's texts putting them in curly braces (for instance {a}, {b} or {d}). This is true not only for the Question text but also for all feedbacks and hints when you use interactive behaviour (The author thinks that the fact that variables can't be used in calculated question's feedback is a serious problem to give students an appropriate feedback using the values they saw in their attempt)

• Another big advantage of formulas questions is that a question can have several 'parts' and all parts using the same variables; and even more, the answer to each part can not only be a number but a vector if you want.
• Last thing, formulas questions has a complete unit system that is quite useful for engineering

## Translations available

This plugin is also available in Mexican Spanish

## Examples

• After you install the plugin, there is a sample-formulas-questions.xml file, with several examples of formulas questions in the 'moodle/question/type/formulas/sample' folder. You can use the Import questions option (Moodle XML) to put them into your Question bank, in order to see how they work.

## Drawbacks

• Mastering formulas questions is difficult, there is a learning curve
• Documentation is not very good, it was written by Hon Wai Lo (original author of the formulas questions for Moodle 1.9 and 2.0, Jean-Michel Védrine upgraded it for Moodle 2.3 to 2.8), unfortunately Jean-Michel Védrine never had time to improve it
• It's a Moodle plugin, so you must install it (or your administrator must do it). Currently formulas question type plugin is not available in the Moodle plugins Directory, you must download it from the author's Github repository. And you must install another plugin (Tim Hunt's adaptive multipart behaviour) so that it works.
• As any addon, you will be dependent in the future of the maintainer to upgrade it when a new Moodle version is released

## FAQ

### Is there a way to indicate the number of significant figures in a formulas question?

Dominique Bauer has worked around the fact that sigfig is not (yet) implemented in the Formulas question type by coming up with the following very short variable assignment which works with any real number:

```xr=x==0?x:round(x*pow(10,nsf-1-floor(log10(abs(x)))),0)*pow(10,-nsf+1+floor(log10(abs(x))));
```

where nsf is the number of significant figures. See https://moodle.org/mod/forum/discuss.php?d=274975#p1181946