📚 Year 7 WJEC Economics: Formula & Theorem Quick Reference Handbook | 公式定理速查手册
This quick reference handbook is designed for Year 7 students following the WJEC Economics curriculum. It compiles the essential formulas, theorems and key concepts you need to master, from scarcity and opportunity cost to market forces and business costs. Keep it handy for rapid revision and to deepen your understanding of how the economy works.
本速查手册专为学习WJEC经济课程的七年级学生设计，汇总了从稀缺性、机会成本到市场力量和企业成本等需要掌握的核心公式、定理与关键概念。随身携带，便于快速复习，并加深您对经济运行方式的理解。
1. The Basic Economic Problem & Scarcity | 基本经济问题与稀缺性
The fundamental economic problem exists because resources are scarce while human wants are infinite. Scarcity forces individuals, firms and governments to make choices, as not everything can be produced or consumed. The core inequality that summarises this is: Unlimited Wants > Limited Resources → Scarcity → Choice.
根本的经济问题之所以存在，是因为资源稀缺而人类的欲望无限。稀缺性迫使个人、企业和政府做出选择，因为无法生产和消费所有想要的东西。概括这一核心关系的不等式为：无限欲望 > 有限资源 → 稀缺性 → 选择。
2. Opportunity Cost Principle | 机会成本原理
Opportunity cost is the value of the next best alternative that is given up when a choice is made. It represents the true cost of any decision, not merely the money spent. The formula can be expressed as:
机会成本是指当做出某种选择时所放弃的次优替代方案的价值。它代表了任何决策的真实代价，而不仅仅是花费的金钱。该公式可表达为：
Opportunity Cost = Value of Next Best Alternative Forgone
For example, if a student spends an hour studying economics instead of working at a job earning £6, the opportunity cost of studying is the £6 forgone. Understanding opportunity cost helps ensure that resources are allocated to their most valued uses.
例如，如果一名学生花费一小时学习经济学，而不是去做一份时薪6英镑的工作，那么学习的机会成本便是放弃的那6英镑。理解机会成本有助于确保资源被分配到最有价值的用途上。
3. Factors of Production | 生产要素
The resources used to produce goods and services are classified into four factors of production. They are the inputs for any production process.
用于生产商品和服务的资源被划分为四种生产要素。它们是任何生产过程的投入品。
Land includes all natural resources such as soil, water, minerals and forests. Labour is the human effort, both physical and mental, used in production. Capital refers to man-made goods that help produce other goods and services, such as machinery, tools and factories. Enterprise is the willingness to take risks and organise the other three factors to create output; the entrepreneur makes key business decisions.
土地包括所有自然资源，如土壤、水、矿产和森林。劳动力是生产中所投入的人类体力和脑力劳动。资本指有助于生产其他商品和服务的人造物品，如机器、工具和工厂。企业家才能则是愿意承担风险并组织其他三种要素以创造产出的能力；企业家做出关键的商业决策。
4. Demand and the Law of Demand | 需求与需求定律
Demand is the quantity of a good or service that consumers are both willing and able to purchase at various prices over a given period of time. The Law of Demand states that, all other factors held constant (ceteris paribus), as the price of a good increases, the quantity demanded decreases. This inverse relationship can be written as:
需求是指消费者在一段时间内愿意并能够以不同价格购买的商品或服务的数量。需求定律指出，在其他条件不变的情况下，一种商品的价格上升，其需求量就会下降。这种反比关系可写作：
P↑ → Qd↓ (Price rises → Quantity demanded falls)
The demand curve slopes downwards from left to right. Factors that can shift the entire demand curve include changes in income, tastes, prices of related goods (substitutes and complements) and expectations.
需求曲线从左向右下方倾斜。能够使整条需求曲线移动的因素包括收入变化、品味变化、相关商品（替代品和互补品）价格变化以及预期变化。
5. Supply and the Law of Supply | 供给与供给定律
Supply is the quantity of a good or service that producers are willing and able to offer for sale at different prices over a given period. The Law of Supply states that, ceteris paribus, as the price of a good rises, the quantity supplied increases. This direct relationship can be expressed as:
供给是指生产者在一段时间内愿意并能够以不同价格出售的商品或服务的数量。供给定律指出，在其他条件不变的情况下，商品价格上升，其供给量也会增加。这种正比关系可表达为：
P↑ → Qs↑ (Price rises → Quantity supplied rises)
The supply curve slopes upwards. Factors that shift the supply curve include changes in production costs, technology, taxes and subsidies, and the number of sellers in the market.
供给曲线向上倾斜。使供给曲线移动的因素包括生产成本变化、技术变化、税收与补贴以及市场上卖者的数量。
6. Market Equilibrium | 市场均衡
Market equilibrium occurs at the price where the quantity demanded by consumers exactly equals the quantity supplied by producers. There is no tendency for price to change, provided external factors remain the same. The equilibrium condition is:
市场均衡发生在消费者需求量恰好等于生产者供给量的价格水平上。只要外部因素保持不变，价格就没有变化的趋势。均衡条件为：
Qd = Qs
At prices above equilibrium, a surplus (excess supply) exists, pushing price down. At prices below equilibrium, a shortage (excess demand) drives price up. The intersection of demand and supply curves determines the equilibrium price (Pe) and equilibrium quantity (Qe).
在均衡价格之上，存在过剩（超额供给），迫使价格下降；在均衡价格之下，存在短缺（超额需求），推动价格上升。需求曲线与供给曲线的交点决定了均衡价格（Pe）和均衡数量（Qe）。
7. Total Revenue, Total Cost & Profit | 总收入、总成本与利润
These three formulas are the foundation for understanding a firm's financial performance.
这三个公式是理解企业财务表现的基础。
Total Revenue (TR) is the income a firm receives from selling its output.
总收入（TR）是企业通过销售产出所获得的收入。
TR = P × Q
where P = price per unit, Q = quantity sold.
其中 P = 单位价格，Q = 销售数量。
Total Cost (TC) is the sum of all costs incurred in production.
总成本（TC）是生产中发生的所有费用之和。
TC = FC + VC
where FC = fixed costs, VC = variable costs.
其中 FC = 固定成本，VC = 可变成本。
Profit (π) is the difference between total revenue and total cost. It is the reward for risk-taking.
利润（π）是总收入与总成本之差，是对承担风险的回报。
π = TR − TC
even when TR = TC. If TR > TC, the firm makes a profit; if TR < TC, it makes a loss.
当 TR = TC 时，企业实现盈亏平衡。若 TR > TC，企业盈利；若 TR < TC，企业亏损。
8. Cost Formulas (Fixed, Variable, Total) | 成本公式（固定、可变、总成本）
Costs are categorised by how they behave as output changes in the short run.
成本根据其在短期内随产出变化的方式进行分类。
Fixed Costs (FC) do not vary with the level of output. Examples include rent, insurance and salaries of permanent staff. Even if production is zero, fixed costs must still be paid.
固定成本（FC）不随产量水平变化。例子包括租金、保险和固定员工的工资。即使产量为零，仍需支付固定成本。
Variable Costs (VC) change directly with output. Examples are raw materials, packaging and energy used in production. As output rises, variable costs increase; as output falls, they decrease.
可变成本（VC）直接随产量变化。例子有原材料、包装和生产用能源。产量上升，可变成本增加；产量下降，可变成本减少。
TC = FC + VC
Average Fixed Cost (AFC) and Average Variable Cost (AVC) help to understand the cost per unit:
平均固定成本（AFC）和平均可变成本（AVC）有助于理解每单位成本：
AFC = FC ÷ Q
AVC = VC ÷ Q
9. Average Cost | 平均成本
Average Total Cost (ATC), often simply called average cost, measures the cost of producing a typical unit of output. It is crucial for pricing decisions.
平均总成本（ATC），通常简称为平均成本，衡量生产一个典型单位产出的成本。它对定价决策至关重要。
ATC = TC ÷ Q
Or, because TC = FC + VC, the formula can also be written as:
或者，因为 TC = FC + VC，该公式也可写作：
ATC = AFC + AVC
As output increases, AFC falls continuously because the same fixed cost is spread over more units. AVC typically falls initially due to efficiencies, then may rise as production becomes more stretched. The U-shaped ATC curve reflects these changes. A firm aims to set a price that covers ATC in the long run to remain profitable.
随着产出增加，AFC持续下降，因为相同的固定成本被分摊到更多单位上。AVC最初往往因效率提高而下降，随后可能因生产变得紧张而上升。U形的ATC曲线反映了这些变化。从长远看，企业设定的价格必须覆盖ATC才能保持盈利。
10. Money and Functions of Money | 货币及其职能
Money is any asset that is generally accepted as a means of payment. It performs four essential functions in a modern economy. While not a formula, these functions are fundamental theorems of how a monetary economy works.
货币是任何被普遍接受的支付手段。它在现代经济中履行四项基本职能。尽管不是公式，但这些职能是关于货币经济如何运行的基本定理。
- Medium of exchange: Money eliminates the need for barter, allowing people to trade goods and services easily.
- 交换媒介：货币消除了以物易物的需要，使人们能够便捷地交换商品和服务。
- Unit of account: Money provides a standard measure for stating and comparing the value of goods and services.
- 计价单位：货币提供了一个用于表示和比较商品与服务价值的标准尺度。
- Store of value: Money can be saved and used to transfer purchasing power into the future, provided inflation remains low.
- 价值储藏：货币可以被储蓄并用来将购买力转移到未来，前提是通货膨胀保持低位。
- Standard of deferred payment: Money allows debts to be expressed and repaid over time using an agreed unit.
- 延期支付标准：货币使得债务可以按照约定的单位长期记录和偿还。
For money to function well, it must be durable, portable, divisible, scarce and generally acceptable.
货币要良好地运转，必须具备耐用、便携、可分割、稀缺和广泛接受的特征。
Published by TutorHao | Economics Revision Series | aleveler.com
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