📚 Formula and Theorem Quick Reference Handbook | 公式定理速查手册
Economics is the study of how people make choices when resources are limited. This handbook lists the essential formulas, laws and concepts you need for Year 8 Cambridge Economics, clearly explained in both English and Chinese. Use it to revise key topics such as scarcity, demand and supply, elasticity, costs and profit.
经济学研究人们在资源有限时如何做出选择。本手册列出了Year 8剑桥经济学所需的核心公式、定律和概念，并用中英双语进行清晰解释。可用于复习稀缺性、需求与供给、弹性、成本与利润等重要主题。
1. The Economic Problem | 经济问题
The basic economic problem is that resources are scarce but human wants are unlimited. Scarcity forces individuals, firms and governments to make choices about what to produce, how to produce and for whom to produce.
基本经济问题是资源稀缺而人类欲望无限。稀缺性迫使个人、企业和政府做出选择，决定生产什么、如何生产以及为谁生产。
2. Factors of Production | 生产要素
Economists classify resources into four factors of production: land (natural resources), labour (human effort), capital (man-made goods used to produce other goods) and enterprise (the willingness to take risks and combine the other three factors).
经济学家将资源分为四种生产要素：土地（自然资源）、劳动力（人力付出）、资本（用于生产其他产品的人造物品）和企业精神（承担风险并结合其他三种要素的意愿）。
| Factor | 要素 | Examples |
|---|---|---|
| Land | 土地 | Oil, forests, water |
| Labour | 劳动力 | Workers, teachers |
| Capital | 资本 | Machines, tools |
| Enterprise | 企业精神 | Risk-taking, innovation |
3. Opportunity Cost | 机会成本
Opportunity cost is the value of the next best alternative that is given up when a choice is made. It is not always measured in money. For example, if you spend one hour studying instead of going out with friends, the opportunity cost is the enjoyment you would have gained from being with your friends.
机会成本是指做出一项选择时所放弃的次优替代品的价值。它不总是用金钱衡量。例如，如果你花一小时学习而不是和朋友出去玩，机会成本就是你从与朋友相处中本可获得的乐趣。
4. Demand and the Law of Demand | 需求与需求定律
Demand is the willingness and ability of consumers to buy a good at a given price in a given time period. The law of demand states that, ceteris paribus (all other factors unchanged), as the price of a good rises, the quantity demanded falls, and vice versa.
需求指消费者在给定时间和价格下愿意并能够购买商品的意愿与能力。需求定律指出，在其他条件不变的情况下，商品价格上升时需求量下降，价格下降时需求量上升。
5. Supply and the Law of Supply | 供给与供给定律
Supply is the willingness and ability of producers to sell a good at a given price in a given time period. The law of supply states that, ceteris paribus, as the price of a good rises, the quantity supplied increases, and as price falls, quantity supplied decreases.
供给指生产者在给定时间和价格下愿意并能够出售商品的意愿与能力。供给定律指出，在其他条件不变的情况下，商品价格上升时供给量增加，价格下降时供给量减少。
6. Market Equilibrium | 市场均衡
Market equilibrium occurs when quantity demanded equals quantity supplied. At the equilibrium price there is no shortage or surplus. If the price is above equilibrium, a surplus (excess supply) exists; if below, a shortage (excess demand) occurs.
市场均衡发生在需求量等于供给量时。在均衡价格下，没有短缺或过剩。如果价格高于均衡，会出现过剩（超额供给）；如果低于均衡，会出现短缺（超额需求）。
7. Price Elasticity of Demand (PED) | 需求价格弹性
Price elasticity of demand measures how responsive the quantity demanded is to a change in price. The formula is:
需求价格弹性衡量需求量对价格变化的反应程度。公式为：
PED = % change in quantity demanded / % change in price
If PED > 1, demand is elastic (sensitive to price). If PED < 1, demand is inelastic (less sensitive). Note: Year 8 usually works with simple labels; you do not need to calculate exact values in most exams.
如果 PED > 1，需求富有弹性（对价格敏感）。如果 PED < 1，需求缺乏弹性（不太敏感）。注：Year 8 通常只需要记住标签，多数考试不要求精确计算。
8. Price Elasticity of Supply (PES) | 供给价格弹性
Price elasticity of supply measures how responsive the quantity supplied is to a change in price. The formula is:
供给价格弹性衡量供给量对价格变化的反应程度。公式为：
PES = % change in quantity supplied / % change in price
When PES > 1, supply is elastic. When PES < 1, supply is inelastic. Factors such as production time and spare capacity affect PES.
当 PES > 1 时，供给富有弹性；当 PES < 1 时，供给缺乏弹性。生产时间、闲置产能等因素影响供给弹性。
9. Costs, Revenue and Profit | 成本、收入与利润
Total cost is the sum of fixed and variable costs. Total revenue is the money a firm receives from sales. Profit is the difference between total revenue and total cost. The key formulas are:
总成本是固定成本与变动成本之和。总收入是企业从销售中获得的款项。利润是总收入与总成本之差。关键公式包括：
TC = FC + VC
TR = P × Q
Profit = TR − TC
meaning zero profit. Profit maximisation occurs when the gap between TR and TC is largest.
当总收入等于总成本时，企业盈亏平衡，利润为零。利润最大化发生在总收入与总成本差距最大时。
10. Types of Economic Systems | 经济体系类型
Three main types of economic systems exist: market economy (decisions made by private individuals and firms through the price mechanism), planned economy (decisions made by the government), and mixed economy (a combination of both). Most modern economies are mixed.
存在三种主要的经济体系：市场经济（由私人和企业通过价格机制做决策）、计划经济（由政府做决策）和混合经济（两者结合）。大多数现代经济体都是混合经济。
- Market economy: relies on supply and demand.
- Planned economy: central planning allocates resources.
- Mixed economy: public and private sectors both play roles.
- 市场经济：依靠供给与需求。
- 计划经济：中央计划分配资源。
- 混合经济：公共和私人部门都发挥作用。
11. Functions of Money | 货币的职能
Money serves four main functions in an economy: a medium of exchange (used to buy goods and services), a unit of account (allows prices to be compared), a store of value (can be saved and used later), and a standard of deferred payment (used for borrowing and lending).
货币在经济中发挥四种主要职能：交换媒介（用于购买商品和服务）、记账单位（便于比较价格）、价值储藏（可以储蓄以备将来使用）和延期支付标准（用于借贷）。
12. Specialisation and Division of Labour | 专业化与分工
Specialisation means concentrating on a particular task or product. Division of labour breaks down a production process into simple, separate tasks, each done by a different worker. Benefits include increased productivity and efficiency. However, workers may become bored, and the output depends on everyone’s contribution.
专业化指专注于某特定任务或产品。分工将生产过程分解为简单、独立的环节，由不同工人完成。好处包括提高生产率和效率。但工人可能感到枯燥，且产出依赖于每个人的贡献。
- Advantages: higher output, lower costs, skill development.
- Disadvantages: monotony, interdependence, loss of craft skills.
- 优势：产出更高、成本更低、技能发展。
- 劣势：单调乏味、相互依赖、手艺技能丧失。
Published by TutorHao | Economics Revision Series | aleveler.com
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