Formula & Theorem Quick Reference for KS3 OCR Economics | KS3 OCR 经济：公式定理速查手册

📚 Formula & Theorem Quick Reference for KS3 OCR Economics | KS3 OCR 经济：公式定理速查手册

This revision handbook brings together the essential formulae, theorems, and key definitions that KS3 OCR Economics students need at their fingertips. It covers scarcity, demand and supply, elasticity, costs, money, and macroeconomic indicators, all presented in clear English–Chinese pairs. Use it to test yourself, complete homework, and prepare confidently for assessments.

本复习手册汇集了 KS3 OCR 经济学学生必须掌握的核心公式、定理与关键定义，涵盖稀缺性、需求与供给、弹性、成本、货币以及宏观经济指标，全部以清晰的中英对照呈现。用它来检测自己、完成作业，并为考试做好充分准备。

1. Scarcity, Choice and Opportunity Cost | 稀缺性与选择及机会成本

Scarcity is the fundamental economic problem: resources are limited, but human wants are unlimited.

稀缺性是基本经济问题：资源是有限的，但人类的欲望是无限的。

Because of scarcity, individuals, firms, and governments must make choices. Every choice involves giving something up.

由于稀缺性，个人、企业和政府必须做出选择。每个选择都涉及放弃某些东西。

The opportunity cost is the value of the next best alternative that is forgone when a decision is made.

机会成本是指做出一项决定时所放弃的下一个最优选择的价值。

Opportunity Cost = Value of the Next Best Alternative Forgone

机会成本 = 放弃的下一个最佳选择的价值

Opportunity cost is not measured only in money; it includes time, enjoyment, and any other benefit you lose.

机会成本不仅仅以金钱衡量，还包括时间、快乐以及你失去的任何其他好处。

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2. Factors of Production and Their Rewards | 生产要素及其报酬

Economists classify resources into four factors of production: land, labour, capital, and enterprise.

经济学家将资源分为四种生产要素：土地、劳动力、资本和企业家才能。

Each factor earns a specific reward: land earns rent, labour earns wages, capital earns interest, and enterprise earns profit.

每种要素获得特定的报酬：土地获得地租，劳动力获得工资，资本获得利息，企业家才能获得利润。

Factor → Reward: Land → Rent | Labour → Wages | Capital → Interest | Enterprise → Profit

要素 → 报酬：土地 → 地租 | 劳动 → 工资 | 资本 → 利息 | 企业家 → 利润

The quantity and quality of factors of production affect a country’s productive potential.

生产要素的数量和质量影响一个国家的生产潜力。

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3. The Law of Demand | 需求定律

The law of demand states that, ceteris paribus, as the price of a good rises, the quantity demanded falls, and vice versa.

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，反之亦然。

This inverse relationship is shown by a downward-sloping demand curve.

这种反向关系表现为一条向下倾斜的需求曲线。

Demand Law: Price ↑ ⇒ Quantity Demanded ↓ (ceteris paribus)

需求定律：价格 ↑ ⇒ 需求量 ↓ （其他条件不变）

A change in the good’s own price causes a movement along the demand curve. Changes in other factors—such as income, tastes, or the price of related goods—shift the entire demand curve.

商品自身价格的变化引起沿需求曲线的移动。其他因素的变化——如收入、偏好或相关商品的价格——会使整条需求曲线移动。

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4. The Law of Supply | 供给定律

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。

This positive relationship gives an upward-sloping supply curve.

这种正向关系形成一条向上倾斜的供给曲线。

Supply Law: Price ↑ ⇒ Quantity Supplied ↑ (ceteris paribus)

供给定律：价格 ↑ ⇒ 供给量 ↑ （其他条件不变）

Shifts in supply occur when factors such as production costs, technology, or the number of sellers change.

当生产成本、技术或卖方数量等因素发生变化时，供给曲线会发生移动。

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5. Market Equilibrium | 市场均衡

Market equilibrium occurs where the quantity demanded equals the quantity supplied. At this point, there is no tendency for the price to change.

市场均衡发生在需求量等于供给量之处。在这一点上，价格没有变动的趋势。

The equilibrium price and quantity can be found at the intersection of the demand and supply curves.

均衡价格和均衡数量可以在需求曲线与供给曲线的交点处找到。

Equilibrium: Quantity Demanded (Qd) = Quantity Supplied (Qs)

均衡：需求量 (Qd) = 供给量 (Qs)

If the market price is above equilibrium, a surplus exists. If it is below equilibrium, a shortage occurs.

若市场价格高于均衡价格，会出现过剩；若低于均衡价格，则会出现短缺。

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6. Price Elasticity of Demand (PED) | 需求价格弹性

Price elasticity of demand measures how responsive quantity demanded is to a change in price.

需求价格弹性衡量需求量对价格变动做出反应的程度。

PED = Percentage Change in Quantity Demanded ÷ Percentage Change in Price

PED = 需求量变动百分比 ÷ 价格变动百分比

PED is usually negative because price and quantity demanded move in opposite directions, but economists often look at the absolute value.

PED 通常为负值，因为价格与需求量呈反方向变动，但经济学家通常看其绝对值。

PED Value | PED 值	Elasticity Type | 弹性类型
|PED| > 1	Elastic | 富有弹性
|PED| < 1	Inelastic | 缺乏弹性
|PED| = 1	Unit Elastic | 单位弹性

Goods with many substitutes or that take a large share of income tend to have more elastic demand.

替代品多或占收入比重大的商品，其需求往往更富有弹性。

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7. Total Revenue | 总收益

Total revenue (TR) is the money a firm receives from selling its goods or services.

总收益是企业通过销售商品或服务获得的货币收入。

Total Revenue (TR) = Price per unit (P) × Quantity sold (Q)

总收益 (TR) = 单位价格 (P) × 销售量 (Q)

If demand is elastic, a price cut raises total revenue; if demand is inelastic, a price rise raises total revenue.

如果需求富有弹性，降价会增加总收益；如果需求缺乏弹性，提价会增加总收益。

Revenue does not equal profit—firms must also deduct their costs.

收益不等于利润——企业还必须扣除其成本。

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8. Costs and Profit | 成本与利润

Total cost (TC) is the sum of all expenses a firm incurs in production. It includes fixed costs (FC), which do not vary with output, and variable costs (VC), which do.

总成本是企业生产中所产生的全部费用之和。它包括不随产量变动的固定成本 (FC) 和随产量变动的可变成本 (VC)。

Total Cost (TC) = Fixed Cost (FC) + Variable Cost (VC)

总成本 (TC) = 固定成本 (FC) + 可变成本 (VC)

Average cost (AC) is the cost per unit of output:

平均成本 (AC) 是每单位产出的成本：

Average Cost (AC) = Total Cost ÷ Quantity

平均成本 (AC) = 总成本 ÷ 产量

Profit is what remains after all costs are subtracted from total revenue.

利润是从总收益中扣除所有成本后剩余的部分。

Profit = Total Revenue (TR) − Total Cost (TC)

利润 = 总收益 (TR) − 总成本 (TC)

A firm may have normal profit (just covering opportunity cost) or supernormal profit (above that level).

企业可能有正常利润（刚好弥补机会成本）或超额利润（高于该水平）。

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9. Functions of Money | 货币的功能

Money is not just coins and notes—it must perform four key functions in an economy.

货币不仅仅是硬币和纸币——它必须在经济中履行四项关键功能。

• Medium of exchange: money is accepted to buy and sell goods and services, removing the need for barter.

  交换媒介：货币被接受用于买卖商品和服务，消除了物物交换的需要。

• Unit of account: money provides a common measure of the value of different goods and services.

  记账单位：货币为不同商品和服务的价值提供了共同的衡量标准。

• Store of value: money can be saved and used in the future, although inflation can erode its purchasing power.

  价值储藏：货币可以储存起来将来使用，尽管通货膨胀会侵蚀其购买力。

• Standard of deferred payment: money allows debts and future obligations to be stated and settled.

  延期支付标准：货币使债务和未来义务能够标明并得以清偿。

These functions make trade, saving, and planning much easier for households, businesses, and the government.

这些功能让家庭、企业和政府的交易、储蓄和规划都变得更加容易。

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10. Interest Rates and Saving | 利率与储蓄

The interest rate is the reward for saving and the cost of borrowing. It is usually expressed as a percentage per year.

利率是储蓄的回报，也是借款的成本。它通常以年百分率表示。

When interest rates rise, saving becomes more attractive and borrowing becomes more expensive.

当利率上升时，储蓄变得更有吸引力，借款则变得更加昂贵。

Economists distinguish between nominal interest rate and real interest rate.

经济学家区分名义利率和实际利率。

Real Interest Rate ≈ Nominal Interest Rate − Inflation Rate

实际利率 ≈ 名义利率 − 通货膨胀率

The real interest rate tells you how much your purchasing power grows; if inflation is higher than the nominal rate, savers lose out in real terms.

实际利率告诉你购买力增长了多少；如果通货膨胀率高于名义利率，储户的实际购买力就会受损。

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11. Economic Growth | 经济增长

Economic growth refers to an increase in the amount of goods and services produced in a country over time. It is commonly measured by the percentage change in real Gross Domestic Product (GDP).

经济增长是指一个国家在一段时间内生产的商品和服务数量的增加。它通常用实际国内生产总值 (GDP) 的百分比变动来衡量。

Economic Growth Rate = [(GDP in Year 2 − GDP in Year 1) ÷ GDP in Year 1] × 100%

经济增长率 = [(第2年GDP − 第1年GDP) ÷ 第1年GDP] × 100%

Sustained economic growth can raise living standards, but it may also create environmental costs if not managed carefully.

持续的经济增长可以提高生活水平，但如果管理不善，也可能产生环境代价。

Growth can be caused by increases in the factors of production or by improvements in productivity and technology.

经济增长可能由生产要素的增加或生产率和技术的改进引起。

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12. Inflation | 通货膨胀

Inflation is a sustained rise in the general price level of goods and services in an economy over time.

通货膨胀是指一个经济体中商品和服务的总体价格水平在一段时间内持续上涨的现象。

The most common measure is the Consumer Price Index (CPI). Inflation rate is calculated as:

最常见的衡量指标是消费者价格指数 (CPI)。通货膨胀率的计算方法为：

Inflation Rate = [(CPI₂ − CPI₁) ÷ CPI₁] × 100%

通货膨胀率 = [(本期CPI − 上期CPI) ÷ 上期CPI] × 100%

A low and stable inflation rate is usually a government target (e.g., 2%). High inflation reduces the real value of money and can hurt people on fixed incomes.

低而稳定的通货膨胀率通常是政府的目标（例如 2%）。高通胀会降低货币的实际价值，并可能损害固定收入人群的利益。

Deflation, a sustained fall in the general price level, can be equally harmful as it may delay spending and investment.

通货紧缩，即总体价格水平的持续下降，可能同样有害，因为它会导致支出和投资推迟。

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Published by TutorHao | Economics Revision Series | aleveler.com

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