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Using the calculation filter with free-text inputs

The free-text input allows students to embed calculations within their answer. Rather than reaching for a separate calculator, students can request the result of a calculation client-side using Javascript.

This document gives an example question using this feature. See the filter calculations reference documentation for the various calculation options.

Question variables

Notice in the teacher's answer ta1 they use calculations. Of course, this is simple, but it is just an example.

ta1:castext("The consecutive even numbers are `n` and `n+2`.  Their difference is 2
`
n + (n+2) = 45*2
2n + 2 = {#45*2#}
2n = {#(45*2)-2#}
n = {#((45*2)-2)/2#}
`
Note this is an even number.
");
ta2:(45*2-2)/2;

Question text

<p>Find the smaller of two consecutive even numbers such that their sum is \(45\) times there difference.</p>
<p>Work line by line below, justifying your answer fully.</p>
<div class="free-text-container">
[[input:ans1]] [[validation:ans1]]
[[ascii input="ans1"]]
  [[filter type="calculation" /]]
  [[filter type="markdown-math" transforms="aligneq" /]]
  [[extractor targetinput="ans2" type="lastexpr"/]]
[[/ascii]]
</div>
<p>[[commonstring key="free_text_calc"/]]</p>
<p style="display:none">[[input:ans2]]</p>
<p>[[validation:ans2]]</p>

The [[filter]] blocks specify how the student's input is processed.

The first type="calculation" extracts {@...@} as requested calculations and replaces this with the answer.

The second is type="markdown-math" which processes the (updated) text as Markdown with AsciiMath support. This explicit block is needed because the default markdown-math filter is only provided when no filters are explicitly defined in the block. The filter order matters, and here the question author needs to specify that calculation comes before markdown-math.

Lastly, the final expression is sent to a numerical input.

Inputs

Input ans1 holds the free-text.

  • Change input ans1 from the algebraic (default) to free-text.
  • Change the input "Input box size" to 80 or 100, to give more space to type.
  • Change "Student must verify" to no, and "Show the validation" to no.
  • Extra options: monospace:true, manualgraded:false

Input ans2 holds the final answer.

  • No special changes for ans2.

PRT

Students might enter a number, e.g. 44 or an equation n=44, so to accommodate both define the following in the feedback variables.

sa2:if equationp(ans2) then rhs(ans2) else ans2

Set up the PRT to compare sa2 with ta2. Algebraic equivalence is fine in this simple example.

The PRT could be improved to check for common mistakes, and add feedback.

General feedback

You can use the value of ta1 to create a worked solution in the general feedback, with a static version of the [[ascii]] block.

[[ascii]]{@ta1@}[[/ascii]]

This question can also be loaded from 

Doc-Examples/Specialist-Tools-Docs/Free-text-input/Free-text_with_calculation.xml