Many IB Mathematics: Applications & Interpretation students are surprised when exam questions explicitly allow approximation in sequence problems. After years of being trained to find exact answers, being told that an approximate value is acceptable can feel unsettling or even suspicious. Students often worry that approximation means they are “doing maths wrong.”
IB allows approximation deliberately. The goal is to test whether students understand behaviour, trends, and modelling, not whether they can force exact arithmetic when it is unrealistic or unnecessary.
What Approximation in Sequences Is Really Testing
When IB allows approximation, it is shifting focus away from precision and toward interpretation.
In real-world contexts, sequences often represent:
- Financial growth over long periods
- Population changes
- Repeated processes or iterations
- Models where exact values are impossible
IB expects students to recognise that beyond a certain point, exact values add little insight. Approximation is used to understand what is happening, not to avoid thinking.
Why Exact Answers Become Impractical
Many sequences grow or shrink very quickly.
For large values of n, exact arithmetic can become:
- Time-consuming
- Calculator-dependent
- Difficult to interpret meaningfully
IB allows approximation so students can focus on scale, growth rate, and long-term behaviour instead of struggling with unwieldy numbers.
Why This Appears More in AI Than AA
Applications & Interpretation prioritises modelling and realism.
IB expects AI students to behave like real analysts, not symbolic calculators. In real modelling, exact values are rarely known or even useful. Approximation reflects how mathematics is used outside the classroom.
This is why approximation is not only accepted but often encouraged in AI exams.
Why Students Feel Uncertain Using Approximation
Most students associate approximation with losing marks.
IB reverses this expectation. Students often lose marks by:
- Forcing exact calculations unnecessarily
- Refusing to approximate when instructed
- Over-rounding without explanation
- Failing to interpret approximate results
Approximation becomes risky only when it is used without judgement or justification.
How IB Decides What Is Acceptable
IB examiners look for:
- Reasonable rounding
- Consistency with given data
- Clear interpretation
- Awareness of limitations
Approximate answers are marked correct when they show sound reasoning, even if they differ slightly from another student’s result.
Common Student Mistakes
Students frequently:
- Avoid approximation when allowed
- Approximate too early
- Use inconsistent accuracy
- Fail to explain what the approximation shows
- Treat approximation as guessing
Most mistakes come from discomfort with uncertainty.
Exam Tips for Approximation in Sequences
Read the question carefully for permission to approximate. Keep precision during calculations and round sensibly at the end. Focus on interpreting trends rather than chasing exact values. Use language like “approximately” or “about” — IB rewards this clarity.
Frequently Asked Questions
Does approximation mean exact answers are wrong?
No. It means exact answers are unnecessary. IB values insight over precision in these cases.
How accurate should my approximation be?
As accurate as the context allows. IB expects reasonable judgement, not extreme precision.
Can different students get different answers?
Yes — and both can be correct if the reasoning is sound. IB allows tolerance when interpretation is strong.
RevisionDojo Call to Action
Approximation is not a weakness — it’s a modelling skill. RevisionDojo helps IB Applications & Interpretation students learn when approximation is appropriate, how to justify it, and how examiners assess it. If approximation questions feel risky or unclear, RevisionDojo is the best place to build confident mathematical judgement.
