This topic covers the basic problem of economics: resources are limited, wants are not, so choices must be made and every choice has a cost. It is the foundation for Economics and appears in short-answer, data-response and longer questions.
Check the current syllabus on the Cambridge page for your exam year, then use this module as a study route.
What should you know first?
You do not need earlier Economics. You should be comfortable reading a table, subtracting, and dividing a loss by a gain. Three words matter from the start: scarcity (limited resources), choice and opportunity cost (the next most valued alternative given up).
An orienting example
Tanjung Island, a fictional economy, makes only boats and rice. It can make 30 boats and 36 tonnes of rice, or 40 boats and 20 tonnes of rice.
Moving from the first to the second gains 10 boats and loses 16 tonnes of rice. The opportunity cost is 1.6 tonnes of rice per boat.
That one calculation uses scarcity (it cannot have both), choice (it picks a mix) and opportunity cost (the rice lost). The lessons below unpack each piece.
In what order should you study the lessons?
- Identify the next most valued alternative: the core idea, and the one most often written wrongly.
- Distinguish a want from an effective demand: shows why limited incomes matter to markets.
- Classify a productive resource: names the four resources that scarcity applies to.
- Explain a movement on a production possibility model: puts opportunity cost on a diagram.
- Interpret an outward shift without claiming all groups benefit: adds balanced evaluation.
After the lessons, try the mixed practice set. Then continue to specialisation and allocation.
What traps catch students here?
- Giving every rejected option as the opportunity cost, instead of only the next most valued one.
- Using price or money spent as the cost.
- Writing “demand” when the question describes only a want.
- Calling money capital.
- Giving the level at a point on the PPC rather than the change between points.
- Saying an outward shift means everyone gains.
How should you use the practice set?
Attempt it after the lessons, on paper, and mark errors by type. The set ends with a table that routes each error type back to the right lesson. Keep notes in the mistake log and retest queue, and retest after a few days.
If opportunity cost still comes out wrong in your written answers, a teacher in online one-to-one Economics tuition can check each sentence with you.