📚 Year 10 Cambridge Economics: Formula & Theorem Quick Reference Handbook | Year 10 Cambridge 经济：公式定理速查手册
This handbook compiles all the essential formulas and theorems you need to master for the Year 10 Cambridge Economics syllabus. Each section is presented in clear pairings of English and Chinese explanations, helping you revise efficiently and understand key economic relationships.
本手册汇集了 Year 10 Cambridge 经济课程中必须掌握的所有重要公式与定理。每个部分都以英文和中文解释的对照形式呈现，帮助你高效复习并理解关键的经济学关系。
1. Scarcity and Opportunity Cost | 稀缺性与机会成本
Scarcity is the fundamental economic problem: finite resources cannot satisfy infinite human wants. Because of scarcity, choices must be made, and every choice involves an opportunity cost.
稀缺性是经济学的基本问题：有限的资源无法满足无限的人类欲望。由于稀缺性，必须做出选择，而每一个选择都涉及机会成本。
Opportunity Cost = Value of the next best alternative foregone
机会成本是指所放弃的次优选择的价值。它提醒我们决策的真实代价不仅仅是货币支出。
2. Law of Demand and Law of Supply | 需求定律与供给定律
The law of demand states that, ceteris paribus, as the price of a good rises, the quantity demanded falls, and vice versa. There is an inverse relationship between price and quantity demanded.
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。价格与需求量之间存在反向关系。
The law of supply states that, ceteris paribus, as the price of a good rises, the quantity supplied expands, and vice versa. There is a direct relationship between price and quantity supplied.
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，反之亦然。价格与供给量之间存在正向关系。
3. Market Equilibrium and Disequilibrium | 市场均衡与非均衡
Market equilibrium occurs at the price where quantity demanded equals quantity supplied. There is no tendency for price to change at this point, which clears the market.
市场均衡发生在需求量等于供给量的价格水平。在这个点上价格没有变动的趋势，市场出清。
If the market price is above equilibrium, a surplus (excess supply) exists, pushing price downwards. If the market price is below equilibrium, a shortage (excess demand) exists, pulling price upwards.
如果市场价格高于均衡价格，会出现过剩（超额供给），推动价格下降。如果市场价格低于均衡价格，会出现短缺（超额需求），推动价格上升。
4. Price Elasticity of Demand (PED) | 需求价格弹性
Price elasticity of demand measures the responsiveness of quantity demanded to a change in price. It is always negative due to the law of demand, but we often use its absolute value.
需求价格弹性衡量需求量对价格变化的反应程度。由于需求定律，它总是负值，但我们常使用其绝对值。
PED = %ΔQd ÷ %ΔP
公式：需求量变化百分比除以价格变化百分比。
If PED < 1, demand is price inelastic (unresponsive). If PED = 1, demand is unit elastic.
如果 PED > 1，需求是富有价格弹性的（反应灵敏）；如果 PED < 1，需求是缺乏价格弹性的（反应迟钝）；如果 PED = 1，需求具有单位弹性。
5. PED and Total Revenue | 需求价格弹性与总收益的关系
Total revenue (TR) is the amount a firm receives from sales. The relationship between PED and TR guides pricing decisions.
总收益是企业从销售中获得的总金额。PED 与总收益的关系指导定价决策。
TR = Price × Quantity
总收益等于价格乘以销售量。
When demand is elastic (PED > 1), a price decrease raises total revenue because the percentage increase in quantity demanded is larger than the percentage fall in price.
当需求富有弹性时（PED > 1），降价会增加总收益，因为需求量增加的百分比大于价格下降的百分比。
When demand is inelastic (PED < 1), a price increase raises total revenue because the percentage fall in quantity demanded is smaller than the percentage rise in price.
当需求缺乏弹性时（PED < 1），提价会增加总收益，因为需求量减少的百分比小于价格上升的百分比。
6. Price Elasticity of Supply (PES) | 供给价格弹性
Price elasticity of supply measures the responsiveness of quantity supplied to a change in price. It is usually positive because of the positive relationship between price and quantity supplied.
供给价格弹性衡量供给量对价格变化的反应程度。由于价格与供给量的正向关系，它通常为正值。
PES = %ΔQs ÷ %ΔP
公式：供给量变化百分比除以价格变化百分比。
If PES > 1, supply is price elastic (producers can respond quickly). If PES < 1, supply is price inelastic (producers face difficulties adjusting output).
如果 PES > 1，供给是富有弹性的（生产者能快速反应）；如果 PES < 1，供给是缺乏弹性的（生产者调整产出有困难）。
7. Income Elasticity of Demand (YED) | 需求收入弹性
Income elasticity of demand measures the responsiveness of demand for a good to a change in consumers' income. It helps classify goods as normal or inferior.
需求收入弹性衡量商品需求对消费者收入变化的反应程度。它有助于区分正常品和低档品。
YED = %ΔQd ÷ %ΔY
公式：需求量变化百分比除以收入变化百分比。
For normal goods, YED is positive (demand rises as income rises). For inferior goods, YED is negative (demand falls as income rises). Luxury goods have YED > 1, while necessities have 0 < YED < 1.
对于正常品，YED 为正（收入增加需求上升）；对于低档品，YED 为负（收入增加需求下降）。奢侈品 YED > 1，必需品 YED 在 0 到 1 之间。
8. Cross Elasticity of Demand (XED) | 需求交叉弹性
Cross elasticity of demand measures the responsiveness of demand for one good to a change in the price of another good. It identifies substitutes and complements.
需求交叉弹性衡量一种商品的需求对另一种商品价格变化的反应程度。它用于识别替代品和互补品。
XED = %ΔQd of good A ÷ %ΔP of good B
公式：商品 A 的需求量变化百分比除以商品 B 的价格变化百分比。
If XED is positive, the two goods are substitutes (e.g. tea and coffee). If XED is negative, they are complements (e.g. printers and ink cartridges).
如果 XED 为正，两种商品是替代品（如茶和咖啡）；如果 XED 为负，它们是互补品（如打印机和墨盒）。
9. Costs, Revenue and Profit | 成本、收益与利润
Firms must understand their cost structures to make production decisions. Key formulas link total, average and per-unit concepts.
企业必须了解成本结构以做出生产决策。关键公式将总量、平均量和单位概念联系起来。
TC = TFC + TVC
总成本等于总固定成本加总可变成本。
AFC = TFC ÷ Q AVC = TVC ÷ Q
平均固定成本等于总固定成本除以产量；平均可变成本等于总可变成本除以产量。
ATC = TC ÷ Q = AFC + AVC
平均总成本等于总成本除以产量，也等于平均固定成本加平均可变成本。
Profit = TR – TC
利润等于总收益减去总成本。经济利润考虑了机会成本。
10. Law of Diminishing Marginal Utility | 边际效用递减定律
The law of diminishing marginal utility states that as a consumer consumes additional units of a good, the extra satisfaction (marginal utility) gained from each additional unit eventually decreases.
边际效用递减定律指出，随着消费者消费某商品的数量增加，每额外消费一单位所带来的额外满足感（边际效用）最终会递减。
This helps explain the downward-sloping demand curve: consumers are only willing to buy more if the price falls, because the additional utility from further units is lower.
这有助于解释需求曲线向下倾斜的原因：消费者只愿意在价格下降时购买更多，因为额外单位带来的效用更低。
11. Production Possibility Curve (PPC) | 生产可能性曲线
A production possibility curve shows the maximum combinations of two goods an economy can produce with its given resources and technology. It illustrates opportunity cost and efficiency.
生产可能性曲线展示了一个经济体在给定资源和技术下能生产的两种商品的最大组合。它说明了机会成本和效率。
Points on the curve represent full and efficient use of resources; points inside indicate unemployed or inefficient resources; points outside are unattainable with current resources.
曲线上点代表资源充分有效利用；曲线内的点表明资源未充分利用或无效；曲线外的点在当前资源下无法达到。
Opportunity cost increases as production shifts along a bowed-out PPC (law of increasing opportunity cost).
当沿着向外弯曲的 PPC 转移生产时，机会成本递增（机会成本递增定律）。
12. Measuring the Economy: Inflation and Unemployment | 经济测量：通货膨胀与失业率
Macroeconomic indicators help assess economic performance. Two key measures are the inflation rate and the unemployment rate.
宏观经济指标有助于评估经济表现。两个关键指标是通货膨胀率和失业率。
Inflation Rate = (CPI current – CPI previous) ÷ CPI previous × 100
通货膨胀率等于（当年消费物价指数 － 上年消费物价指数）除以上年消费物价指数，再乘以 100。
Unemployment Rate = (Number of unemployed ÷ Labour force) × 100
失业率等于（失业人数除以劳动力总数）再乘以 100。
The labour force includes those employed and those actively seeking work. These formulas are essential for analysing economic stability.
劳动力包括就业者和积极寻找工作的人。这些公式对分析经济稳定性至关重要。
Published by TutorHao | Economics Revision Series | aleveler.com
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