📚 Year 7 CAIE Economics Formula and Theorem Quick Reference Handbook | Year 7 CAIE 经济：公式定理速查手册
Welcome to your essential quick-reference guide for Year 7 CAIE Economics. This handbook brings together the most important formulas, definitions, and theorems you will encounter, from the basic economic problem to market forces and simple quantitative tools. Use it to reinforce your understanding and build strong foundations for future studies.
欢迎使用 Year 7 CAIE 经济学核心速查手册。本手册汇总了你将遇到的最重要的公式、定义和定理，从基本经济问题到市场力量以及简单的量化工具。用它来巩固理解，为未来学习打下坚实基础。
1. The Basic Economic Problem and Scarcity | 基本经济问题与稀缺性
The fundamental economic problem arises because human wants are unlimited, but resources are finite. Scarcity forces every society to answer three key questions: What to produce? How to produce? For whom to produce? These choices lie at the heart of economics.
基本经济问题的根源在于人类的欲望是无限的，而资源是有限的。稀缺性迫使每个社会回答三个关键问题：生产什么？如何生产？为谁生产？这些选择是经济学的核心。
2. Opportunity Cost Formula | 机会成本公式
Every choice involves a trade-off. The opportunity cost of a decision is the value of the next best alternative that you give up. Understanding this concept helps individuals and businesses make rational choices.
每一个选择都涉及权衡。一项决策的机会成本是你所放弃的次优选择的价值。理解这一概念有助于个人和企业做出理性选择。
Opportunity Cost = Value of the Next Best Alternative Foregone
机会成本 = 放弃的次优选择的价值
If you have £10 and choose to buy a book instead of a cinema ticket, the opportunity cost of the book is the enjoyment you would have gained from the movie. Opportunity cost is not always measured in money; it can be time, pleasure, or any lost benefit.
如果你有10英镑，选择买书而不是电影票，那么买书的机会成本就是你本可以从电影中获得的享受。机会成本不一定用金钱衡量；它可以是时间、快乐或任何失去的好处。
3. Factors of Production | 生产要素
Resources used to produce goods and services are grouped into four factors of production: land, labour, capital, and enterprise. Each factor earns a reward: land earns rent, labour earns wages, capital earns interest, and enterprise earns profit.
用于生产商品和服务的资源分为四种生产要素：土地、劳动力、资本和企业。每种要素获得相应的报酬：土地获得地租，劳动力获得工资，资本获得利息，企业获得利润。
Land refers to all natural resources. Labour is the human effort, both physical and mental. Capital includes man-made tools and machinery. Enterprise is the ability to combine the other three factors and take risks. The quality and quantity of these factors determine a country’s productive capacity.
土地指所有自然资源。劳动力是人类的体力和脑力劳动。资本包括人造的工具和机械。企业则是将其他三种要素组合并承担风险的能力。这些要素的质量和数量决定了一个国家的生产能力。
4. Law of Demand and Demand Curve | 需求定律与需求曲线
The law of demand states that, ceteris paribus (all other things being equal), as the price of a good rises, the quantity demanded falls, and vice versa. This inverse relationship gives the demand curve its downward slope.
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，反之亦然。这种反向关系使得需求曲线向右下方倾斜。
A demand schedule shows how much consumers are willing to buy at different prices. The market demand is the sum of all individual demands. Factors that shift the demand curve include changes in income, tastes, prices of related goods (substitutes and complements), and population size.
需求表显示了消费者在不同价格下愿意购买的数量。市场需求是所有个人需求的总和。导致需求曲线移动的因素包括收入变化、偏好变化、相关商品（替代品和互补品）的价格变化以及人口规模的变化。
5. Law of Supply and Supply Curve | 供给定律与供给曲线
The law of supply indicates that, ceteris paribus, as the price of a good rises, the quantity supplied increases. Producers are motivated by higher prices to offer more for sale, so the supply curve slopes upward.
供给定律表明，在其他条件不变的情况下，一种商品的价格上升，其供给量就会增加。更高的价格激励生产者提供更多产品，因此供给曲线向右上方倾斜。
The supply curve can shift due to changes in production costs, technological advancements, taxes and subsidies, and the number of sellers. If a new technology reduces manufacturing expenses, supply increases, shifting the curve to the right.
供给曲线可能因生产成本变化、技术进步、税收和补贴以及卖者数量变化而发生移动。如果新技术降低了生产成本，供给增加，曲线向右移动。
6. Market Equilibrium and Price Mechanism | 市场均衡与价格机制
Market equilibrium occurs where the quantity demanded equals the quantity supplied. The price at this intersection is the equilibrium price, and the corresponding quantity is the equilibrium quantity. The price mechanism naturally moves the market towards this balance.
市场均衡发生在需求量等于供给量之处。交点对应的价格是均衡价格，对应的数量是均衡数量。价格机制自然而然地引导市场走向这一平衡。
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 occurs, pushing prices down. If the price is below equilibrium, a shortage arises, pushing prices up. This self-correcting feature is called the invisible hand.
如果市场价格高于均衡，就会出现剩余，推动价格下降。如果价格低于均衡，则出现短缺，推动价格上升。这种自我修正的特性被称为“看不见的手”。
7. Price Elasticity of Demand (PED) – Basic Concept | 需求价格弹性基本概念
Price elasticity of demand measures how responsive the quantity demanded is to a change in price. It helps firms predict how a price change might affect their total revenue.
需求价格弹性衡量需求量对价格变化的反应程度。它帮助企业预测价格变化可能如何影响其总收益。
PED = (% Change in Quantity Demanded) ÷ (% Change in Price)
需求价格弹性 = 需求量变动百分比 ÷ 价格变动百分比
If PED > 1, demand is elastic: quantity changes more than price. If PED < 1, demand is inelastic: quantity changes less than price. If PED = 1, demand is unit elastic. Necessities often have inelastic demand, while luxury goods tend to be elastic.
如果PED > 1，需求富有弹性：数量变化大于价格变化。如果PED < 1，需求缺乏弹性：数量变化小于价格变化。如果PED = 1，需求为单位弹性。必需品往往缺乏弹性，而奢侈品通常富有弹性。
8. Quantity Theory of Money (Simplified) | 货币数量论（简化版）
The quantity theory of money explains the connection between the amount of money in an economy and the general price level. In its simplest form, it states that an increase in the money supply leads to a proportional increase in prices, assuming velocity and output remain constant.
货币数量论解释了经济中货币量与总体价格水平之间的联系。在最简单的形式中，它说明在流通速度和产出不变的情况下，货币供应量的增加会导致价格同比例上升。
Equation of Exchange: M × V = P × T
交易方程式：M × V = P × T
Here, M is the money supply, V is the velocity of circulation, P is the average price level, and T is the volume of transactions. For Year 7, remember that injecting more money without more goods tends to cause inflation.
其中，M 是货币供应量，V 是货币流通速度，P 是平均价格水平，T 是交易量。对于 Year 7 学生，记住如果没有更多的商品而注入更多货币，往往会引发通货膨胀。
9. Types of Costs: Fixed, Variable, and Total | 成本类型：固定成本、可变成本与总成本
Businesses must understand their costs to set prices and earn profits. Fixed costs (FC) remain constant regardless of output, such as rent. Variable costs (VC) change with the level of production, like raw materials. Total cost (TC) is the sum of both.
企业必须了解自身成本才能定价和赚取利润。固定成本 (FC) 不随产出变化而保持不变，例如租金。可变成本 (VC) 随生产水平变化，例如原材料。总成本 (TC) 是两者之和。
Total Cost = Fixed Cost + Variable Cost (TC = FC + VC)
总成本 = 固定成本 + 可变成本 (TC = FC + VC)
Another important concept is total revenue (TR), which equals the selling price per unit multiplied by the quantity sold. Profit is found by subtracting total cost from total revenue. If TR > TC, the business makes a profit.
另一个重要概念是总收益 (TR)，它等于单位售价乘以销售数量。利润等于总收益减去总成本。如果 TR > TC，企业就盈利。
10. Savings and Investment Basics | 储蓄与投资基础
Savings represent the part of income not spent on consumption. Individuals save for future purchases, emergencies, or retirement. Banks channel savings into investments, which are spending on capital goods that can increase future production.
储蓄代表收入中没有用于消费的部分。个人为未来的购买、紧急情况或退休而储蓄。银行将储蓄引导到投资中，后者是用于能提高未来产出的资本品的支出。
The simple saving ratio can be calculated as: Saving ratio = (Savings ÷ Income) × 100%. A higher saving ratio can boost funds available for investment, but overly high saving reduces current consumption, which may slow down economic activity.
简单的储蓄率可以这样计算：储蓄率 = (储蓄额 ÷ 收入) × 100%。较高的储蓄率可以增加可用于投资的资金，但过高的储蓄会减少当前消费，可能减缓经济活动。
Published by TutorHao | Economics Revision Series | aleveler.com
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