This assigns the value 4 to $x only if the condition $a == 2 is true. In the Common Control environment, this shorthand syntax works for simple one-line conditionals.

For more complex logic, you can use a full if...else structure like this:

This checks whether $a is greater than 10 and assigns a value to $x accordingly.

You can declare different input types for each part of a multipart problem using strings like "number", "choices", "multans" (multiple answer checkboxes), "calculated" (MathQuill input), "string", or "essay" Each entry in the array corresponds to one part of the question.

This controls how much each part of a multipart question contributes to the total score. For example, $answeights = array(0.5, 0.5); means the first part will be worth 50% of the points and the second 50%. You can also assign different weights, like array(0.4, 0.4, 0.2) — here, the first two parts are each worth 40% and the third is worth 20%.

If the problem has only one part or answer box, you can simply use $answer = "5";. For multipart problems, use indexed answers like $answer[0] for the first part, $answer[1] for the second part, and so on. Each value should match the corresponding $anstypes definition.

The $choices array defines the answer options for a multiple-choice question. In a multipart problem, each index corresponds to one part: for example, $choices[0] provides the choices for $answerbox[0], while $choices[2] defines the choices for the third part of the problem ($answerbox[2]). Be sure each $choices[x] array matches the corresponding $anstypes[x] as "choices".

The $displayformat setting controls how the student's answer is shown in the answer box. Common options include:

• "decimal" – Displays the input as a plain decimal number (default for numerical questions).
• "mixednumber" – Allows or requires a mixed number format like 1 1/2.
• "fraction" – Displays a proper or improper fraction like 3/4 or 7/5.
• "scinot" – Displays numbers in scientific notation (e.g., 3.2e5).
• "sigfig" – Enforces a specific number of significant figures (requires $sigfigs to be set).
• "logic" – For logical expressions (true/false logic).
• "list" – For list-style answers (e.g., entering multiple numbers separated by commas).
• "string" – For free-response string input (used with $anstypes = "string").
• "typein" – A basic text box (used with "string" type).
• "noinput" – Hides the answer box entirely (used for display-only questions).

Choose the format that best matches your question's expectations and grading method.

This setting enforces that a student’s answer is entered with a specific number of decimal places. For example, $reqdecimals = 2; means all answers must have exactly 2 decimal places. To require precision on just one part of a multipart question, use an index like $reqdecimals[1] = 3; to enforce 3 decimals on only the second part.

This sets how far a student's numerical answer can deviate from the correct answer and still be marked correct. For example, $abstolerance = 0.01; allows answers within ±0.01 of the correct value. For multipart questions, you can apply it to just one part using an index like $abstolerance[0] = 0.05;.

This sets the tolerance as a percentage of the correct answer, rather than a fixed amount. For example, $reltolerance = 0.001; allows answers within 0.1% of the correct value. To apply this to only one part of a multipart question, use an index like $reltolerance[2] = 0.01; to allow a 1% margin on the third part.

The loadlibrary() function allows you to bring in additional macros and functions that expand what you can do in the Common Control section. You can load multiple libraries at once by separating them with commas, like loadlibrary("stats,fractions");.

For example, the "stats" library gives you access to functions such as:

• mean(array) – Computes the mean of a data set
• stdev(array) – Computes the standard deviation
• percentile(array, p) – Finds a percentile
• histogram(array,...) – Generates histogram display data
• linreg(xarray, yarray) – Performs linear regression

Another useful library is "fractions", which enables fraction-specific operations and representations (like handling reduced forms). Load only the libraries you need to keep your problem lightweight and avoid unnecessary function conflicts.

This generates a random integer value between 1 and 10, inclusive: $x = rand(1, 10);

To generate a random number between 1 and 10 to one decimal place, you can do: $x = rand(10, 100) / 10;
This generates a random integer from 10 to 100 and then divides by 10 to produce values like 1.2, 7.5, or 9.8.

This technique is useful when you want to generate decimal values (floats) with consistent formatting for use in real-world contexts like prices, measurements, probabilities, or statistical data. For example, $r = rand(100, 200)/100; produces values between 1.00 and 2.00, which are commonly needed in statistics, economics, and applied math problems.

This code selects a random value from the $alphas array. The expression rand(0,2) generates a random index (0, 1, or 2), and $alphas[...] retrieves the corresponding value — in this case, one of 0.01, 0.05, or 0.10.

To randomly select multiple values from an array, you can shuffle the array and then pick the first few elements. For example: $alphas = array(0.01, 0.05, 0.10, 0.15);
shuffle($alphas);
$alpha1 = $alphas[0];
$alpha2 = $alphas[1]; This randomly selects two distinct alpha values from the original list.

This code uses diffrands(1,10,2) to generate two different random integers between 1 and 10. The values are stored in $a and $b. This is useful when you need multiple values that are guaranteed to be distinct.

This code rounds the value of $r to 2 decimal places and stores the result in $z. You can also use rounding directly in the answer declaration, such as $answer = round($r, 2); for a single-part problem, or $answer[0] = round($r, 3); to round to 3 decimal places in a multipart problem.

includecodefrom(1610504) pulls in the Common Control code from problem ID 1610504, which defines a variable called $css. This variable contains embedded CSS styling for custom classes you can use inside the Question Text section, such as:

• .problem-mom – for boxed problem containers
• .note-mom – for highlighted instructions or notes
• .alist-mom – for styled answer lists
• .redtext-mom – for emphasized red warning text

In the Question Text section, you must place $css as the very first line — it should appear alone, with no HTML tags around it. This is required for the styles to load properly.

Here’s an example of how your Question Text might look:

These styles help create consistency and visual polish across custom MyOpenMath problems.