Why Does Approximation Feel Subjective in IB Maths?
Many IB Mathematics: Applications & Interpretation students feel uncomfortable with approximation because it seems to lack clear rules. Unlike algebra, where answers are exact, approximation requires decisions: how much to round, which value to use, and how precise a result should be. This makes approximation feel subjective and risky in exams.
IB includes approximation intentionally. The goal is to test mathematical judgement, not just calculation. In real-world contexts, exact answers rarely exist, and IB expects students to reason sensibly about uncertainty rather than chase false precision.
What Approximation Is Really About
Approximation is about choosing a value that is reasonable given the context.
IB expects students to recognise that:
- Data is often measured, not exact
- Models simplify reality
- Results have limits of accuracy
Approximation reflects how confident we can be in an answer. This is why it appears so often in modelling, finance, statistics, and applied calculus questions.
Why Approximation Has No Single “Correct” Answer
In many IB questions, more than one approximation may be acceptable.
What matters is whether the approximation is justified. IB examiners look for consistency between:
- The accuracy of the data
- The method used
- The final answer
Two students may give slightly different answers and both be correct if their reasoning is sound.
Why This Feels Uncomfortable for Students
Most earlier maths education rewards exact answers.
Applications & Interpretation deliberately moves away from this. IB wants students to explain why an answer makes sense, not just what the answer is. This shift from certainty to reasoning is what makes approximation feel subjective.
How IB Decides What Is Acceptable
IB does not mark approximation arbitrarily.
Examiners consider:
- Whether rounding matches data accuracy
- Whether approximation is delayed until the end
- Whether interpretation acknowledges uncertainty
- Whether conclusions are cautious
Marks are awarded for good judgement, not guesswork.
Where Approximation Appears Most Often
Approximation is central in:
- Financial modelling
- Statistical summaries
- Regression and prediction
- Error and bounds
- Applied calculus
These topics rely on interpretation more than exactness.
Common Student Mistakes
Students frequently:
- Over-round results
- Under-round to appear “exact”
- Apply different accuracy at different steps
- Ignore context when approximating
- Assume only one correct value exists
Most mistakes come from fear of being wrong, not lack of understanding.
Exam Tips for Approximation Questions
Read context carefully. Match accuracy to data quality. Delay rounding until the final step. Use cautious language such as “approximately” or “about.” If unsure, justify your choice — IB rewards explanation.
Frequently Asked Questions
Can two different answers both be correct?
Yes, if both are justified and consistent. IB allows reasonable tolerance when interpretation is sound.
Why does IB avoid exact answers in AI Maths?
Because real-world problems are rarely exact. IB wants students to model reality, not idealised numbers.
How do I know if my approximation is acceptable?
Check whether it aligns with the precision of the given data. If it does, and you can explain it, it is usually acceptable.
RevisionDojo Call to Action
Approximation feels subjective only when judgement isn’t taught clearly. RevisionDojo helps IB Applications & Interpretation students learn how examiners think about accuracy, uncertainty, and justification. If approximation questions feel risky or unpredictable, RevisionDojo is the best place to build confidence and control.
