中文（繁體）
中文（简体）
English
S4 Economics: Opportunity Cost and the PPC – Error-Correction Practice (10 Questions)
S4 Economics: Opportunity Cost and the PPC – Error-Correction Practice (10 Questions)
Ten items target the usual slips: opportunity cost taken as money paid, forgone options added together, confusions over inside and outside the curve, average and marginal cost mixed up, comparative advantage read from output, and sunk costs still counted.
Quick answer 1. $300; 2. $5000; 3. efficient on the curve, underused inside; 4. 1 unit of Y; 5. 1.5 units of Y, rising; 6. only (1) and (2); 7. A makes X and B makes Y at a rate between 0.5 and 1; 8. yes, a net gain of 300; 9. it is not money paid; 10. only $5000.
01 Paper details (check answers afterwards)
| Item | Detail |
|---|---|
| Questions | 10 questions |
| Suggested time | about 25 minutes |
| Difficulty mix | Foundation 3 · Intermediate 3 · Challenge 2 · Error redo 2 |
| Chapter | Chapter: S4 Economics | Opportunity Cost and the PPC: error-correction practice |
| Level | S4 |
02 Questions (10 items)
- FoundationA film ticket costs $80 and travel $20; the three hours could earn $200 from tutoring. What is the opportunity cost of going?
- FoundationOne plot can earn $3000 from vegetables, $5000 from rice or $4000 from chickens. If the owner grows vegetables, what is the opportunity cost?
- FoundationWhat does a point on the production possibility curve show, compared with a point inside it?
- IntermediateOn a country production possibility curve point A is (0 X, 120 Y) and point B is (30 X, 90 Y). Moving from A to B, what is the average opportunity cost of each unit of X?
- IntermediateFrom B (30 X, 90 Y) the country moves to C (50 X, 60 Y). What is the marginal opportunity cost per unit of X on this segment, and how does it compare with A to B?
- IntermediateWhich of these shifts the whole production possibility curve outward? (1) technical progress (2) more workers (3) a higher price for the good
- ChallengeCountry A can make 4 X or 2 Y per hour; country B can make 3 X or 3 Y per hour. Which good should each specialise in, and within what range must the world exchange rate lie for both to gain?
- ChallengeA course deposit of $500 is paid and non-refundable. You may pay a further $1500 to finish, after which the course is worth $1800 to you. On marginal grounds, should you pay?
- Error redoA student writes that opportunity cost is simply the money paid for something. What is wrong?
- Error redoA plot can grow vegetables ($3000), rice ($5000) or keep chickens ($4000), and a student says the opportunity cost of vegetables is $12000. What is wrong?
03 Answers and one-line notes
| # | Answer | One-line note |
|---|---|---|
| 1 | $300: the $80 ticket, the $20 fare and the $200 income forgone. | Opportunity cost adds up every value given up, not just the ticket price. |
| 2 | $5000. | Only the single best forgone option counts; the three incomes are never added together. |
| 3 | On the curve resources are fully and efficiently used; inside the curve they are not fully used, with unemployment or waste. | A point inside allows more of one good without giving up the other, so it is inefficient. |
| 4 | 1 unit of Y: 30 units of Y given up for 30 units of X. | Average opportunity cost equals Y given up divided by X gained. |
| 5 | 1.5 units of Y (30 divided by 20), higher than 1 unit on the previous segment, so marginal opportunity cost is rising. | The curve bows outward precisely because each extra segment costs more Y. |
| 6 | Only (1) and (2); (3) does not change productive capacity. | Price is a market outcome, while the curve moves only when resources or technology change. |
| 7 | A specialises in X at 0.5 Y each, below B at 1 Y; B specialises in Y. The rate must lie between 0.5 and 1 unit of Y per unit of X. | Comparative advantage looks at opportunity cost, not at output size. |
| 8 | Yes: $1500 more buys $1800 of value, a net gain of $300, and the $500 deposit is sunk. | Only future benefits and costs matter; money already paid and unrecoverable is irrelevant. |
| 9 | Opportunity cost is the value of the best forgone alternative; money is only one form, and time or effort count too. | Equating opportunity cost with money spent is the commonest conceptual slip in this topic. |
| 10 | The three incomes were added together; only the best forgone option, $5000, counts. | Summing every forgone option is the second commonest error here. |
04 What to do after marking
- After marking, redo only the wrong items and write down which step went wrong (formula, unit, or misread number).
- Repeat the same item two days later; move to the next paper only when both attempts are correct.
- Parents only need the answer and note columns; there is no need to explain every item.
Find a tutor freeTutor Registration →
Questions and answers are written originally by the TutorZone team and are not taken from any school, publisher or examination authority paper. Every value is checked by computer.