📚 Case Study Practice for Year 7 Economics | Year 7 经济案例实战演练
In Year 7 CIE Economics, case studies help you apply concepts like scarcity, opportunity cost, demand and supply to real-life situations. This revision guide provides step-by-step practice with common scenarios you might see in assessments. Each example is followed by model analysis in both English and Chinese so you can master the technique of tackling case study questions.
在Year 7 CIE经济学中，案例分析帮助你运用稀缺性、机会成本、需求与供给等概念分析现实情境。这份复习指南通过常见场景的逐步练习，带你掌握解答案例题型的方法。每个示例都配有中英对照的示范分析，让你彻底掌握应对案例分析的技巧。
1. What is a Case Study in Economics? | 什么是经济学案例分析？
A case study in economics presents a short story or scenario about a person, business or government making a decision. Your task is to identify the economic problem, explain why a choice must be made and use key terms such as 'scarcity', 'trade-off' and 'opportunity cost' to support your reasoning. The scenario may involve limited money, time or resources.
经济学中的案例分析通常是一段关于个人、企业或政府做决策的短故事。你的任务是找出经济问题，解释为什么必须做出选择，并用“稀缺性”、“权衡”和“机会成本”等关键术语来支撑你的推理。场景中往往涉及有限的金钱、时间或资源。
Unlike simple definition questions, case studies ask you to apply your knowledge. That means you need to read the story carefully, pick out the constraints and choices, and then explain what the best option would be according to economic thinking. Your answer should be in full sentences and use the evidence from the text.
与单纯的定义题不同，案例分析要求你运用知识。这意味着你需要仔细阅读故事，找出限制条件和选项，然后根据经济学思维解释最佳选择是什么。你的答案应该用完整的句子，并引用文中的证据。
2. Step-by-Step Approach to Tackle a Case | 一步步解决案例的方法
Follow these four steps to build a clear and logical response to any case study question. Each step is explained first in English, then in Chinese.
遵循以下四个步骤，可以让你针对任何案例分析题写出清晰、有逻辑的答案。每个步骤先提供英文解释，再给出中文说明。
Step 1: Identify the scarce resource. Look for what is limited – it could be time, money or materials. For instance, 'John only has £5' or 'A factory has only 10 workers'. Highlight this in the case.
第一步：识别稀缺资源。 找出什么资源是有限的——可以是时间、金钱或原材料。例如，“约翰只有5英镑”或者“一家工厂只有10名工人”。在案例中做标记。
Step 2: List the competing choices. What are the two or more options the person is facing? Write them down using the exact details from the case, e.g. 'buy a book or a snack'.
第二步：列出相互竞争的选项。 这个人面临的两个或多个选择是什么？用案例中的准确细节写下来，例如，“买一本书或一个零食”。
Step 3: Determine the trade-off and opportunity cost. The trade-off is the option you give up. The opportunity cost is the next best alternative forgone. Always phrase it as 'The opportunity cost of choosing X is the benefit lost from not having Y.'
第三步：确定权衡和机会成本。 权衡就是你放弃的选项。机会成本是所放弃的次优选择的价值。始终用这样的表述：“选择X的机会成本，是放弃Y所带来的好处。”
Step 4: Justify your recommended choice. Use economic reasoning, such as greater utility, lower cost or higher profit. Always link back to the concept of scarcity or rational choice.
第四步：为你推荐的选项提供理由。 运用经济学推理，例如效用更大、成本更低或利润更高。一定要将理由与稀缺性或理性选择的概念联系起来。
3. Case 1: Alex's Weekend Choice (Scarcity & Opportunity Cost) | 案例1：亚历克斯的周末选择（稀缺与机会成本）
Alex has exactly 4 hours of free time on Sunday afternoon. He can either play video games at home or go cycling with his friend Ben. Playing video games gives him a fun, relaxing time and lets him complete a new level. Cycling improves his fitness and strengthens his friendship with Ben. Alex cannot do both activities because they happen at the same time and Ben is only available for those 4 hours.
亚历克斯周日下午有正好4小时的空闲时间。他可以在家玩电子游戏，或者和好友本一起骑自行车。玩电子游戏能带来轻松愉快的时光，还能通关一个新关卡。骑自行车能提高体能，也增进了他和本的友谊。亚历克斯无法同时进行这两项活动，因为它们同时发生，而本只在这4小时里有空。
Question: What is the scarce resource in this situation? Identify the opportunity cost if Alex chooses to go cycling.
问题：在这个情境中，稀缺资源是什么？如果亚历克斯选择骑自行车，请指出他的机会成本。
Model answer: The scarce resource is Alex's time. Only 4 hours are available, and he must choose between two enjoyable activities. If Alex goes cycling, the opportunity cost is the enjoyment and the achievement of completing the new level he would have gained from playing video games.
参考答案：稀缺资源是亚历克斯的时间。他只有4小时，必须在两项有趣的活动之间做出选择。如果亚历克斯去骑自行车，机会成本就是他本可从玩电子游戏中获得的那种乐趣以及通关带来的成就感。
4. Identifying the Economic Problem in Alex's Case | 识别亚历克斯案例中的经济问题
Every economic case starts with a problem: unlimited wants meet limited resources. In Alex's story, his unlimited want is to enjoy both leisure activities, but his limited resource is time. This forces him to make a choice, which lies at the heart of economics. The problem is not just about which activity is more fun; it is about how to allocate a scarce resource to maximize satisfaction.
每一个经济案例都源于同一个问题：无限的欲望遇上有限的资源。在亚历克斯的故事里，他无限的欲望是享受两种闲暇活动，但有限的资源是时间。这迫使他做出选择，这正是经济学的核心。问题不仅在于哪个活动更有趣，而且在于如何分配稀缺资源以最大化满足感。
From an economic perspective, Alex weighs the benefits of cycling (better health, friendship) against the benefits of gaming (entertainment, progress). He can use the concept of utility to compare how much satisfaction he expects from each. A rational decision-maker picks the option with the highest perceived benefit.
从经济学角度看，亚历克斯需要权衡骑自行车的好处（更健康、友谊）与打游戏的好处（娱乐、通关）。他可以用“效用”概念来比较自己对每个选项的预期满足感。一个理性的决策者会选择感知收益最高的那个选项。
5. Case 2: The School Book Fair (Demand and Supply) | 案例2：学校书展（需求与供给）
Springfield School holds a second-hand book fair. A popular graphic novel series is priced at £3 per book. Within the first hour, all 20 copies are sold, and many students are still asking for them. Meanwhile, a set of old encyclopedias is priced at £5 per volume. Only 2 out of 15 volumes are sold by the end of the day. The librarian is considering changing prices next year.
春田学校举办二手书展。一套热门漫画书每本定价3英镑。在第一个小时里，全部20本就卖光了，还有很多学生在询问。而一套旧百科全书每卷定价5英镑，到当天结束时只卖出2卷（共15卷）。图书管理员正在考虑明年调整价格。
Questions: Explain why the graphic novels experienced a shortage and the encyclopedias a surplus. What would you expect to happen to prices if the market could adjust freely?
问题：解释为什么漫画书出现了短缺而百科全书出现了过剩。如果市场可以自由调整，你预计价格会发生什么变化？
Model answer: At £3, the quantity demanded for graphic novels (well over 20) was much greater than the quantity supplied (only 20). This created a shortage. The encyclopedias, priced at £5, had a very low quantity demanded (only 2) compared to the quantity supplied (15), resulting in a surplus. In a free market, the price of graphic novels would rise to reduce demand and encourage more supply, while the price of encyclopedias would fall to clear the surplus.
参考答案：在3英镑的价位，漫画书的需求量（远超20本）远大于供给量（只有20本），导致了短缺。百科全书定价5英镑，需求量（仅2卷）相对于供给量（15卷）极低，产生了过剩。在自由市场中，漫画书的价格会上升以减少需求并鼓励更多供给，而百科全书的价格会下降以出清过剩。
6. How Price Changes Affect Decisions in the Book Fair | 价格变化如何影响书展中的决策
When the price of a good changes, both buyers and sellers adjust their behaviour. Suppose next year the librarian sets the graphic novel price at £4. According to the law of demand, some students who were willing to buy at £3 might now find it too expensive and choose not to buy. On the supply side, more students might be encouraged to donate their used graphic novels if they receive a higher price, increasing quantity supplied.
当商品价格发生变化时，买卖双方都会调整行为。假设明年图书管理员将漫画书价格定为4英镑。根据需求定律，一些本来愿意付3英镑的学生可能觉得太贵而不买了。在供给方面，如果售价更高，更多学生也许愿意捐出二手漫画书，从而增加供给量。
For the encyclopedias, lowering the price to £2 might attract buyers who see it as a bargain. The surplus would shrink as quantity demanded rises. This example shows the role of price as a signal: a high price signals to produce more, while a low price signals to consume more.
对于百科全书，将价格降到2英镑可能吸引觉得划算的买家。随着需求量上升，过剩会减少。这个例子展示了价格作为信号的作用：高价发出“多生产”的信号，低价发出“多消费”的信号。
7. Case 3: Maria's Mobile Game Purchases (Budget Constraints) | 案例3：玛丽亚的手机游戏购买（预算约束）
Maria receives £20 as a gift and wants to spend it all on in-game items for her favourite mobile game. A rare skin costs £10. A mystery loot box costs £5 each. She wants both the skin and as many loot boxes as possible. However, her budget limits her to spending no more than £20. She must decide the best combination of items.
玛丽亚收到了20英镑的礼物，想全部用来买她最爱的手机游戏里的道具。一款稀有皮肤售价10英镑，一个神秘宝箱售价5英镑。她既想要皮肤，又想要尽可能多的宝箱。但她的预算限制她最多只能花20英镑。她需要决定物品的最佳组合。
total utility if a skin provides 50 units of satisfaction and a loot box provides 30 units? (Assume she can buy any whole number of each item, as long as total cost ≤ £20.)
问题：列出玛丽亚可负担的物品组合。假设皮肤带来50单位满足感，每个宝箱带来30单位满足感，哪种组合能带给她最大的总效用？（假设她可以买任意整数数量的物品，只要总花费≤20英镑。）
Combinations: (0 skin, 4 boxes) cost £20, utility 0+4×30=120; (1 skin, 2 boxes) cost £10+£10=£20, utility 50+60=110; (2 skins, 0 boxes) cost £ ot boxes yields the highest total utility (120). However, we must also consider that Maria' by the numbers. In reality, consumers make choices based on their own subjective utility.
可负担组合：(0皮肤, 4宝箱) 费用£20，效用0+4×30=120；(1皮肤, 2宝箱) 费用£10+£10=£20，效用50+60=110；(2皮肤, 0宝箱) 费用£20，效用100+0=100。因此，买0个皮肤和4个宝箱的总效用最高(120)。但我们也必须考虑，玛丽亚对皮肤的偏好可能极强，数字并不能完美体现。现实中，消费者基于自身主观效用来做选择。
8. Applying the Concept of Utility | 应用效用概念
Utility is the satisfaction or benefit a consumer gets from a good or service. In a case study, you often need to explain why a person chooses one option over another even though both are affordable. The answer lies in the marginal utility per pound spent. If the last pound on loot boxes gives more extra satisfaction than the last pound on a skin, a rational consumer buys more loot boxes.
效用是消费者从商品或服务中获得的满足感或好处。在案例分析中，你常常需要解释为什么一个人会在两个都可负担的选项中选某一个。答案在于每英镑带来的边际效用。如果花在宝箱上的最后一英镑带来的额外满足感比花在皮肤上的最后一英镑更多，理性消费者就会多买宝箱。
e marginal utility per pound: for a loot box, each pound yields 30/5 = 6 utility units per £. For a skin, each pound yields 50/10 = 5 utility units per £ al in terms of satisfaction per pound. This explains the result from the previous section.
我们可以计算每英镑的边际效用：对于宝箱，每英镑产生30/5=6单位效用。对于皮肤，每英镑产生50/10=5单位效用。由于6>5，就每英镑带来的满足感而言，宝箱更划算。这解释了上一节的结果。
9. Case 4: Liam's Lemonade Business (Costs and Revenue) | 案例4：利亚姆的柠檬水生意（成本与收入）
Liam sets up a lemonade stand in his neighbourhood. He pays a fixed cost of £5 to rent a table and signboard for the day. Each cup of lemonade costs him £0.30 for lemons, sugar and a paper cup. He sells each cup for £1. Liam wants to know how many cups he must sell just to cover all his costs – this is called the break-even point.
利亚姆在社区摆了一个柠檬水摊。他支付5英镑的固定成本来租用一天的桌子和招牌。每杯柠檬水的可变成本为0.30英镑，用于柠檬、糖和纸杯。他以每杯1英镑出售。利亚姆想知道他必须卖出多少杯才能刚好覆盖所有成本——这就是盈亏平衡点。
Break-even formula: Break-even quantity = Fixed cost ÷ (Price per unit – Variable cost per unit). Plugging in Liam's numbers: £5 ÷ (£1 – £0.30) = £5 ÷ £ of a cup, he needs to sell 8 cups to start making a profit. At 8 cups, total revenue = 8 × £1 = £8; total cost = £5 (fixed) + 8 × £0.30 = £5 + £2.40 = £7.40; profit = £0.60.
盈亏平衡公式：盈亏平衡数量 = 固定成本 ÷ (单位价格 – 单位可变成本)。代入利亚姆的数据：5英镑 ÷ (1英镑 – 0.30英镑) = 5英镑 ÷ 0.70英镑 ≈ 7.14。因为不能卖零星杯，他需要卖出8杯才开始盈利。卖出8杯时，总收入 = 8 × £1 = £8；总成本 = £5固定 + 8 × £0.30 = £5 + £2.40 = £7.40；利润 = £0.60。
10. Calculating Profit and Break-Even Point | 计算利润与盈亏平衡点
To show the break-even analysis clearly, we can use a simple table. Calculating profit at different sales volumes helps Liam decide whether the business is worthwhile. Below is a table summarizing costs, revenue and profit for sales of 5, 8, 10 and 15 cups.
为了清晰展示盈亏平衡分析，我们可以用一个简单的表格。计算不同销量下的利润能帮助利亚姆判断这生意是否值得做。以下是汇总5杯、8杯、10杯和15杯时的成本、收入和利润的表格。
| Cups Sold (Q) | Fixed Cost (£) | Variable Cost (£) | Total Cost (£) | Total Revenue (£) | Profit (£) |
|---|---|---|---|---|---|
| 5 | 5.00 | 1.50 | 6.50 | 5.00 | -1.50 |
| 8 | 5.00 | 2.40 | 7.40 | 8.00 | 0.60 |
| 10 | 5.00 | 3.00 | 8.00 | 10.00 | 2.00 |
| 15 | 5.00 | 4.50 | 9.50 | 15.00 | 5.50 |
Notice how profit turns from negative to positive between 5 and 8 cups. That is why the break-even point is so important – it tells a business the minimum it must sell to avoid a loss. In a case study, always explain what the break-even quantity means for the entrepreneur's decision.
注意利润从5杯时的负数变为8杯时的正数。这就是盈亏平衡点如此重要的原因——它告诉企业为避免亏损需要卖出的最低数量。在案例分析中，要始终解释盈亏平衡量对企业决策意味着什么。
11. Using Graphs and Tables in Case Study Answers | 在案例分析答案中使用图表
When you are asked to analyse data in a case study, presenting information in a table or describing a graph can earn you higher marks. Even if you cannot draw a perfect graph in the exam, you can still describe the relationship shown. For example, 'The table shows that total cost rises more slowly after break-even because fixed cost is spread over more cups.'
当案例分析要求你分析数据时，用表格呈现信息或描述图表能帮你获得更高分数。哪怕考试中画不出完美的图，你仍然可以描述所显示的关系。例如，“表格显示，盈亏平衡之后总成本上升变慢，因为固定成本被更多杯子分摊了。”
In a demand and supply case, you might write: 'At the original price of £3, the demand curve lies to the right of the supply curve at a quantity of 40, indicating a shortage. This would push the price up towards a new equilibrium.' This shows the examiner that you understand how to read the graph without drawing it.
在需求与供给的案例中，你可以这样写：“在原价3英镑的水平，需求曲线在供给曲线的右侧，数量为40，表示存在短缺。这将推动价格上升至新的均衡点。”这向考官展示了你无需画图也能理解图表。
| Price (£) | Quantity Demanded | Quantity Supplied |
|---|---|---|
| 2 | 50
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