Answering Calculation Questions (DP IB Economics): Revision Note

Steve Vorster

Written by: Steve Vorster

Reviewed by: Lisa Eades

Updated on

How to answer IB Economics calculation questions

  • Calculation questions appear mainly in Paper 2 and Paper 3 and are closely linked to AO4 (use and application of skills)

    These questions reward method, accuracy, and interpretation, not speed.

  • Many students lose marks not because they do not understand the concept, but because they skip steps, omit units, or fail to interpret results correctly

What examiners are looking for

  • For calculation questions, examiners expect:

    • a clear and correct method

    • accurate numerical working

    • correct units and rounding

    • and, where required, economic interpretation of the result

Examiner Tips and Tricks

Even if the final answer is incorrect, marks may still be awarded for the correct method

General rules for calculations

  • Always show all workings

  • Write out formulas before substituting numbers

  • Include units in the final answer

  • Round final answers to two decimal places (unless instructed otherwise)

  • Use results from calculations in later questions when relevant

Worked Example

Percentage change

Question

Calculate the percentage change in the price of a good when it rises from $20 to $25. [2]

Sample response

Percentage change formula: ((New - Old) / Old) × 100. Example: ((25 - 20) / 20) × 100 = 25%.

Why this scores full marks

✅ Correct formula shown
✅ Clear substitution and working
✅ Final answer clearly stated

Worked Example

Price elasticity of demand

Question

Calculate the price elasticity of demand (PED) when quantity demanded falls from 80 to 60 units following a price increase from $10 to $12. [4]

Sample response

Calculation of price elasticity of demand: Quantity change is -25%, price change is 20%, resulting in PED of -1.25.

Why this scores full marks

✅ Each step is clearly shown
✅ Correct use of the PED formula
✅ Correct sign and final value

Worked Example

Interpretation

Question

Using your answer to part (a), comment on the elasticity of demand. [2]

Sample response

Text explaining that PED of -1.25 implies price elasticity, with blue highlights on "demand is price elastic" and "accurate interpretation," pink on "greater change" and "appropriate use of terms."

Why this scores full marks

✅ Refers explicitly to the calculated value
✅ Correct interpretation of elasticity
✅ Uses economic terminology accurately

Common mistakes to avoid

  • Writing only the final answer with no workings

  • Forgetting negative signs in elasticity values

  • Omitting units

  • Rounding too early

  • Failing to use calculation results in later evaluative questions

Examiner Tips and Tricks

Treat calculations as evidence, not isolated tasks. In Paper 2 and especially Paper 3, numerical results should support explanation and evaluation wherever possible

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Steve Vorster

Author: Steve Vorster

Expertise: Economics & Business Subject Lead

Steve has taught A Level, GCSE, IGCSE Business and Economics - as well as IBDP Economics and Business Management. He is an IBDP Examiner and IGCSE textbook author. His students regularly achieve 90-100% in their final exams. Steve has been the Assistant Head of Sixth Form for a school in Devon, and Head of Economics at the world's largest International school in Singapore. He loves to create resources which speed up student learning and are easily accessible by all.

Lisa Eades

Reviewer: Lisa Eades

Expertise: Business Content Creator

Lisa has taught A Level, GCSE, BTEC and IBDP Business for over 20 years and is a senior Examiner for Edexcel. Lisa has been a successful Head of Department in Kent and has offered private Business tuition to students across the UK. Lisa loves to create imaginative and accessible resources which engage learners and build their passion for the subject.