Ask a Grade 8 student for the next number in 3, 7, 11, 15 and the answer usually comes straight away. Ask them to explain how the sequence works for the 50th term, or to write a rule that works for any term, and the room often goes quiet. That gap between spotting a pattern and describing it precisely is where many marks in MYP Maths Criterion B are won or lost.
In short, Criterion B rewards a clear conjecture, a test of that conjecture on cases beyond the first few, and a general rule that someone else could use without asking what you meant. Students who practise all three steps, rather than stopping at the first correct number, usually show the clearest reasoning.
What Criterion B is actually asking for
Criterion B is the investigating patterns strand of the MYP mathematics framework. It sits alongside knowing and understanding, communicating, and applying mathematics in real-life contexts. Within it, the work follows a fairly predictable chain: you choose a method, find a pattern, make a conjecture, test it, generalise it, and then justify why it holds.
The command terms matter more than most families expect. Words such as describe, justify and generalise tell the marker what to look for. A correct formula with no reasoning behind it will usually earn less than a slightly untidy investigation that shows how the rule was reached.
Spotting the pattern before reaching for a formula
Start with a table, not an equation. Take a matchstick design where each square adds a fixed number of sticks. Write the term number in one column, the number of sticks in the next, and then the differences between consecutive terms. If the differences are constant, the pattern is linear, and that constant difference is a strong clue to the rule.
Students often jump to a formula too early and miss a second pattern hiding in the differences. A sequence such as 1, 3, 6, 10 has differences of 2, 3, 4, which are not constant, so the rule will involve n squared. Noticing that before guessing saves a lot of wasted attempts.
A helpful habit is to keep a short list of what you have noticed:
- What changes from one term to the next, and by how much?
- What stays the same?
- What does the first term tell you about the starting point?
- Does the pattern look the same from the picture as it does from the numbers?
Writing a general rule that someone else can use
A rule is only general if it works for any term, including ones you have not drawn. Once you have a conjecture such as 3n + 1 for the matchstick pattern, test it on a term far from the start. For term 50, the rule gives 151, and you can check that by counting the structure in a different way.
Then explain why the rule works. In the matchstick example, each new square adds 3 sticks, which is where the 3 in 3n comes from, and the single extra stick is the starting piece. A marker wants to see that link between the picture and the symbols, not just the symbols alone.
Words first, then symbols
Many students can write 3n + 1 but cannot say what n stands for. Try describing the rule in a full sentence first, such as 'the number of sticks is three times the term number, plus one'. Then translate it into algebra. Writing both shows the marker that you understand the variable, not just the notation.
Testing and justifying a conjecture properly
Three matching examples do not prove a rule. Look for a case that breaks it, especially at the edges of the pattern, such as term zero or very large terms. If a counterexample appears, that is useful information. Revise the conjecture, note what changed, and test again. Recording that process is often worth more to a student's Criterion B work than a neat final answer.
Justification can be simple. A diagram that shows why the differences behave as they do, or a short argument about how each step builds on the last, is often enough at middle-school level.
How we practise Criterion B with students
The most useful support we can offer is a teacher who asks 'why?' for every student in the room. In batches of 4 to 8, that happens naturally. Our teachers look for each command term in the work, ask students to justify a rule in their own words, and give feedback against the same criteria the school uses.
We begin with a short diagnostic to see whether a student's gap is in spotting patterns, in writing rules, or in explaining reasoning. The plan then targets that gap through weekly worksheets, with pattern tasks at increasing difficulty, and monthly mock investigations. Parents receive regular updates tracked against the plan, so everyone can see whether the reasoning is improving. Families can read more about our IB MYP tuition programme for Grades 8 to 10, and our blog has further guides on maths investigations.
Frequently Asked Questions
What does MYP Maths Criterion B assess?
Criterion B assesses how well a student investigates patterns. That includes choosing a suitable method, making and testing conjectures, writing a general rule, and justifying why it works. Teachers look for clear reasoning at every stage, so a correct answer with no explanation usually scores lower than a well-argued investigation.
Why do I get the right answer but still lose marks on Criterion B?
Usually the answer is correct but the reasoning is missing or unclear. Markers want to see how the rule was found, why it holds for any term, and what the variables mean. Practise explaining each step in full sentences, and test your rule on a term well beyond the ones given.
How does INACADEMICS help students with pattern and rule tasks?
We keep batches small, so teachers can check each student's reasoning rather than only the final answer. Each student starts with a diagnostic, then works through weekly worksheets and monthly mocks aligned to the MYP rubric. Parents receive regular updates against the plan, so progress on patterns and general rules stays visible.
If your child is finding Criterion B hard, book free counselling with our team on +91 9014010410 or WhatsApp us. You can also visit us at 117, 1st Floor, Raichandani Business Bay in Kokapet, above Karachi Bakery. A short conversation is often enough to see where the gap lies and what the next steps should be.